P0482 Cooling Fan Relay 2 Control Circuit

**What Does It Mean?**

This is a generic diagnostic trouble code (DTC) for the powertrain, meaning it covers all makes/models from 1996 onward. However, specific troubleshooting steps vary by vehicle.

If your vehicle’s check engine light comes on and after retrieving the code you find a P0482 displayed, it refers to the engine cooling fan circuit. This is a generic code applying to all OBD-II (On-Board Diagnostic) vehicles.

While you are driving, sufficient air passes through the radiator and effectively cools the engine. When you stop the car, no air passes through the radiator and the engine begins to increase in temperature.

The PCM (Powertrain Control Module) detects the engine temperature increase via the CTS (Coolant Temperature Sensor) located near the thermostat. When the temperature reaches approximately 223 degrees F (the value depends on the make/model/engine), the PCM commands the cooling fan relay to activate the fan. It does this by providing ground to the relay.

There is a problem in this circuit causing the fan not to operate, allowing the engine to overheat while idling or driving at low speeds. When the PCM attempts to activate the fan and monitors the command and the result does not match, the code is set.

NOTE: P0482 refers to the main circuit, however codes P0480 and P0481 concern the same issue, the only difference being they relate to the different fan speed relays.

**Symptoms**

**Symptoms may include:**

* Check Engine Light illuminated (Malfunction Indicator Lamp) and P0482 code set
* Engine temperature increases when the vehicle is stopped and idling

**Potential Causes**

**Causes of this DTC may include:**

* Faulty Fan Control Relay 3
* Fan Control Relay harness is open or shorted
* Poor electrical connections in the circuit
* Faulty Cooling Fan 3
* Faulty Coolant Temperature Sensor
* Cooling Fan Fan harness is open or shorted
* Poor electrical connection in the Cooling Fan circuit
* Intake Air Temperature (IAT) sensor failure
* Air Conditioning Selector
* A/C Refrigerant Pressure Sensor
* Vehicle Speed Sensor (VSS)

**Diagnostic and Repair Procedures**

It is always wise to check the Technical Service Bulletins (TSBs) for your specific vehicle to see what types of complaints have been submitted to dealer service regarding this code. Search using your favorite search engine for “technical service bulletins for …..” Look for the code and the type of repair recommended by the manufacturer. This is also a good idea before purchasing a vehicle.

Many vehicles will have two engine fans, one for engine cooling and the second for air conditioning condenser cooling, and additional cooling for the engine.

The fan that is not in front of the air conditioning condenser is the main cooling fan and the one to focus on initially. Additionally, many vehicles have multi-speed fans requiring up to three fan speed relays for low, medium, and high speeds.

Open the hood and perform a visual inspection. Look at the fan and ensure there is no obstruction in front of the radiator blocking airflow. Spin the fan with your finger (ensure the vehicle and key are off). If it does not spin, the fan bearings are seized and the fan is bad.

Check the electrical connection to the fan. Separate the connector and look for corrosion or bent pins. Repair if necessary and use dielectric grease on the terminals.

Open the fuse box and inspect the cooling fan relay fuses. If they are good, remove the cooling fan relays. The bottom of the fuse box cover will usually indicate the location, but if not, check the owner’s manual.

The function of the vehicle’s PCM is to act as a ground to operate components, not to provide power. The fan relays are nothing more than a remote lighting switch. The fan, along with other devices, draws too much amperage to be safely run into the cockpit, so it is kept under the hood.

A constant power supply from the battery is present on one terminal of each of the relays. This powers the fan when the circuit is closed. A switched power terminal will only be hot when the key is on. The ground terminal of this circuit is the one used when the PCM wants to activate the relay by grounding it.

Look at the circuit diagram printed on the side of the relay. Look for the simple open and closed circuit. Check for the positive battery terminal in the relay block with constant power. The opposite side goes to the fan. Use a test light to find the hot terminal.

Jump the battery terminal to the fan harness terminal and the fan should run. If not, disconnect the fan connection at the fan and using an ohmmeter, check for continuity between the fan side of the relay terminal and the fan connector. If there is continuity, the fan is bad. If not, the harness between the fuse block and the fan is faulty.

If the fan did run, check the relays. Look on the side of the relay for the switched power terminal or simply turn the key on. Check the terminals for another power terminal and see where it would be on the relay.

Jump the battery plus terminal from the first test with this switched terminal and place an additional jumper from the relay’s ground terminal to ground. The switch will click on. Use an ohmmeter to check that the constant battery terminal and the fan harness terminal have continuity, meaning the circuit is closed.

If the circuit did not close or the relay did not click, the relay is bad. Check all relays in the same manner to ensure they all function.

If there was no switched power to the relay, the ignition switch is suspect.

If they prove good, check the CTS with an ohmmeter. Remove the connector. Let the engine cool down and set the ohmmeter to the 200,000-ohm scale. Probe the sensor terminals.

The reading will be around 2.5. For accurate readings, consult a service manual. Accuracy is not necessary as all sensors can be different. You just want to know if it’s working. Plug it back in and warm up the engine.

Stop the engine and pull the CTS plug again. Check it with the ohmmeter, there should be a large change in resistance, if not the sensor is bad.

If the above procedure failed to find a fault, the likelihood is that a bad connection to the PCM or the PCM itself is at fault. Do not proceed further without consulting your service manual. Disconnecting the PCM can cause a loss of programming and the vehicle may not start unless towed to the dealer for reprogramming.

P0483 Cooling Fan Control Malfunction

What does it mean?

This generic powertrain/engine diagnostic code generally applies to all OBDII-equipped engines but appears more frequently in certain Ford, Isuzu, Mazda, Mercedes Benz, and Subaru vehicles.

The cooling fan module is typically mounted behind the radiator in front of the engine. The cooling fan module is usually controlled by the Powertrain Control Module (PCM) based on the inputs wired to it.
The PCM receives these inputs via voltage signals to determine the engine coolant and intake air temperatures, air conditioning pressures, and vehicle speed. This code is set if these inputs do not match the normal operating voltages stored in the PCM’s memory, or if the cooling fan operation does not match the predetermined information stored in the PCM.

P0483 might have been set due to mechanical temperature issues (incorrect coolant temperature due to a stuck thermostat/faulty water pump); or electrical issues (cooling fan circuit failure). These cannot be overlooked during the troubleshooting phase, especially when dealing with an intermittent problem. Troubleshooting steps may vary by manufacturer, cooling fan module type, and wire colors.

Related cooling fan fault codes include:

P0480 Cooling Fan Control Circuit 1 Malfunction
P0481 Cooling Fan Control Circuit 2 Malfunction
P0482 Cooling Fan Control Circuit 3 Malfunction
P0484 Cooling Fan Circuit High Current
P0485 Cooling Fan Power/Ground Circuit Malfunction

Severity and Symptoms

The severity depends on the failure. In case of mechanical failure; severe. In case of electrical failure, it may not be as severe as the PCM can compensate as long as the engine does not overheat. While the PCM compensates, the temperature gauge should be monitored during all driving cycles. Typically, the fans run all the time (100% duty cycle).

Symptoms of a P0483 fault code may include:

Malfunction indicator light illuminated
Engine overheating
Air conditioning system not functioning properly

Potential Causes

Typically, the causes for this code to set are as follows:

Open in the power circuit between the cooling fan module and the PCM – possible
Short to ground in the cooling fan module power circuit – possible
Cooling system malfunction – faulty thermostat/water pump – very likely
Faulty cooling fan module – possible
Faulty PCM – highly unlikely

Diagnostic and Repair Procedures

A good starting point is always to search for a Technical Service Bulletin (TSB) for your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogramming to address this issue, and it is worth checking before discovering you have taken a long/wrong path.

Next, locate the cooling fan module on your specific vehicle. The cooling fan module (cooling fans) is typically mounted behind the radiator in front of the engine. Once located, visually inspect the connectors and wiring. Look for scratches, rubbing, bare wires, burns, or melted plastic. Separate the connectors and carefully inspect the terminals (the metal parts) inside the connectors. See if they appear burned or have a greenish tint indicating corrosion. Use electrical contact cleaner and a plastic bristle brush if terminal cleaning is necessary. Let it dry and apply electrical grease where the terminals make contact.

If you have a scan tool, clear the diagnostic codes from memory and see if P0483 returns. If not, the connections were likely your problem.

If the code returns, check the integrity of the cooling system. Ensure the thermostat and water pump are functioning correctly. Once the engine has cooled, remove the radiator cap and ensure it seals properly on the radiator. If you have doubts about these cooling system components, replace them first, as this is the most common area of concern related to this fault code. Once done, clear the codes and test the vehicle to ensure P0483 does not return.

If the code returns, we will need to test the fans and their associated circuits. Typically, there are 2 wires to each cooling fan module. First, disconnect the wiring harness going to the cooling fan module. With a digital volt ohm meter (DVOM), connect one meter lead to one terminal of one of the fans. Connect the remaining meter lead to the other terminal of the fan. It should not be open or shorted. Check the resistance specifications for your specific vehicle. If the fan motor is open or shorted (infinite resistance or no resistance/0 ohms), replace the cooling fan module or, if available, the cooling fan motor.

If this test passes, with a DVOM, verify that you have 12V at the cooling fan module power circuit (red lead to the fan power circuit, black lead to a good ground). With a scan tool that can activate the cooling fans, turn them on. If there is no 12 volts at the fan, repair the wiring from the PCM or relay to the fan, or possibly a faulty PCM.

If that is okay, check that the cooling fan module is properly grounded. Connect a test light to the positive 12V battery (red terminal) and touch the other end of the test light to the ground circuit going to the cooling fan module circuit ground. Using the scan tool to actuate the cooling fan module, check if the test light illuminates each time the scan tool actuates the fan. If the test light does not illuminate, it would indicate a circuit problem. If it illuminates, wiggle the wiring harness going to the fan to see if the test light flickers, indicating an intermittent connection.

If all tests have passed so far and you continue to get a P0483 code, it would most likely indicate a faulty cooling fan module, although a faulty PCM cannot be ruled out until the fan has been replaced. If in doubt, seek assistance from a qualified automotive diagnostician. PCMs need to be programmed or calibrated to the vehicle to be installed correctly.

P0484 Cooling Fan Circuit Overcurrent

Cooling Fan Circuit High Current

What Does It Mean?

This generic powertrain/diagnostic code applies to all OBDII-equipped engines but appears more frequently in certain Mazda and Mercedes Benz vehicles.

The PCM receives these inputs via voltage signals to determine engine coolant and intake air temperature, air conditioning pressures, and vehicle speed. This code is set if these inputs do not match the normal operating voltages stored in the PCM’s memory, or if the cooling fan operation does not match the predetermined information stored in the PCM.

P0484 is set when too much current is detected during normal fan operation. This can occur during low, medium, or high-speed operation. This also includes vehicles using fan relays to operate the cooling fans. This code only relates to electrical issues (cooling fan circuit malfunction), including intermittent problems. Troubleshooting steps may vary depending on the manufacturer, cooling fan module type, and wire colors.

Related cooling fan malfunction codes include:

P0480 Cooling Fan Control Circuit 1 Malfunction
P0481 Cooling Fan Control Circuit 2 Malfunction
P0482 Cooling Fan Control Circuit 3 Malfunction
P0483 Cooling Fan Rationality Control Malfunction
P0485 Cooling Fan Power/Ground Circuit Malfunction

Severity and Symptoms

Severity depends on the failure. With an electrical failure, it may not be considered severe as the PCM can compensate for it, unless the engine begins to overheat. While the PCM compensates, the temperature gauge should be monitored during all driving cycles. Typically, the fans run all the time (100% duty cycle).

Symptoms of a P0484 trouble code may include:

Malfunction Indicator Light illuminated
Engine overheating
Air conditioning system not functioning properly

Potential Causes

Typically, the causes for this code to set are:

Open or short circuit in the fan control circuit power supply between the cooling fan module and the PCM – possible
Short circuit to ground on the fan control circuit to the cooling fan module – possible
Faulty cooling fan module – most likely
Faulty PCM – least likely

Diagnostic and Repair Procedures

A good starting point is always to search for a Technical Service Bulletin (TSB) for your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogramming to address this issue, and it’s worth checking before discovering you’ve taken a long/wrong path.

Next, locate the cooling fan module on your specific vehicle. The cooling fan module (cooling fans) is typically mounted behind the radiator in front of the engine. Once located, visually inspect the connectors and wiring. Look for scratches, rubbing, exposed wires, burns, or melted plastic. Separate the connectors and carefully inspect the terminals (the metal parts) inside the connectors. See if they appear burnt or have a greenish tint indicating corrosion. Use electrical contact cleaner and a plastic bristle brush if terminal cleaning is necessary. Let it dry and apply electrical grease where the terminals make contact.

If you have a scan tool, clear the diagnostic codes from memory and see if P0484 returns. If not, the connections were likely your problem.

If the code returns, we will need to test the fans and their associated circuits. Typically, there are 2 wires for each cooling fan module. First, disconnect the wiring harness going to the cooling fan module. With a digital volt ohm meter (DVOM), connect one meter lead to one terminal of one of the fans. Connect the remaining meter lead to the other terminal of the fan. It should not be open or shorted. Check the resistance specifications for your specific vehicle. If the fan motor is open or shorted (infinite resistance or no resistance/0 ohms), replace the cooling fan module or, if available, the cooling fan motor.

If this test passes, use a DVOM to verify you have 12V at the cooling fan module power circuit (red lead to the fan power circuit, black lead to a good ground). With a scan tool that can activate the cooling fans, turn them on. If there is no 12 volts to the fan, repair the wiring from the PCM or relay to the fan, or possibly a faulty PCM.

If that checks out, verify the cooling fan module is properly grounded. Connect a test light to the positive 12V battery terminal (red terminal) and touch the other end of the test light to the ground circuit going to the cooling fan module circuit ground. Using the scan tool to actuate the cooling fan module, check if the test light illuminates each time the scan tool actuates the fan. If the test light does not illuminate, it would indicate a circuit problem. If it does illuminate, wiggle the wiring harness going to the fan to see if the test light flickers, indicating an intermittent connection.

If all tests have passed so far and you continue to get a P0484 code, it would most likely indicate a faulty cooling fan module, although a faulty PCM cannot be ruled out until the fan has been replaced. If in doubt, seek assistance from a qualified automotive diagnostician. PCMs need to be programmed or calibrated to the vehicle to be installed correctly.

P0485 Cooling Fan Power/Ground Circuit Malfunction

What does it mean?

This generic powertrain/engine diagnostic code generally applies to all OBDII-equipped engines but appears more frequently in certain Mazda and Mercedes Benz vehicles.

The PCM receives these inputs via voltage signals to determine engine coolant and intake air temperatures, air conditioning pressures, and vehicle speed. This code is set if these inputs do not match the normal operating voltages stored in the PCM’s memory, or if the cooling fan operation does not match the predetermined information stored in the PCM.

P0485 is set when abnormal voltages are detected during normal fan operation on the power/ground side of the cooling fan circuit. This can occur during low, medium, or high-speed operation. This also includes vehicles using fan relays to operate the cooling fans. This code only concerns electrical issues (cooling fan circuit failure), including intermittent problems.

Troubleshooting steps may vary depending on the manufacturer, type of cooling fan module, and wire colors.

Related cooling fan fault codes include:

Severity and Symptoms

The severity depends on the failure. With an electrical failure, it may not be considered severe because the PCM can compensate for it, unless the engine begins to overheat. While the PCM compensates, the temperature gauge should be monitored during all driving cycles. Typically, the fans run all the time (100% duty cycle).

Symptoms of a P0485 fault code may include:

Malfunction indicator lamp illuminated
Engine overheating
Air conditioning system not functioning properly

Potential Causes

Generally, the causes for this code to set are as follows:

Open/short circuit in the fan control circuit power supply between the cooling fan module and the PCM – possible
Short circuit to ground on the fan control circuit to the cooling fan module – possible
Faulty cooling fan module – very likely
Faulty PCM – least unlikely

Diagnostic and Repair Procedures

A good starting point is always to search for a Technical Service Bulletin (TSB) for your specific vehicle. The vehicle manufacturer may have a PCM flash/reprogramming to address this issue, and it’s worth checking before discovering you’ve taken a long/wrong path.

Next, locate the cooling fan module on your specific vehicle. The cooling fan module (cooling fans) is typically mounted behind the radiator in front of the engine. Once located, visually inspect the connectors and wiring. Look for scratches, rubbing, bare wires, burns, or melted plastic. Separate the connectors and carefully inspect the terminals (the metal parts) inside the connectors. Check if they appear burnt or have a greenish tint indicating corrosion. Use electrical contact cleaner and a plastic-bristled brush if terminal cleaning is necessary. Let it dry and apply electrical grease where the terminals make contact.

If you have a scan tool, clear the diagnostic codes from memory and see if P0485 returns. If not, the connections were likely your problem.

For this particular code, this is the most common area of concern, as are the relays/connections to the relays.

If this test passes, use a DVOM to check that you have 12V at the cooling fan module power circuit (red lead to the fan power circuit, black lead to a good ground). With a scan tool that can activate the cooling fans, turn them on. If there is no 12 volts to the fan, repair the wiring from the PCM or relay to the fan, or possibly a faulty PCM.

If that is okay, check that the cooling fan module is properly grounded. Connect a test light to the positive 12V battery (red terminal) and touch the other end of the test light to the ground circuit going to the cooling fan module circuit ground. Using the scan tool to actuate the cooling fan module, check if the light illuminates whenever the scan tool actuates the fan. If the test light does not illuminate, it would indicate a circuit problem. If it lights up, wiggle the wiring harness going to the fan to see if the test light flickers, indicating an intermittent connection.

If all tests have passed so far and you continue to get a P0485 code, it would most likely indicate a faulty cooling fan module, although a faulty PCM cannot be ruled out until the fan has been replaced. If in doubt, seek assistance from a qualified automotive diagnostician. PCMs need to be programmed or calibrated to the vehicle to be installed correctly.

P0486 Exhaust Gas Recirculation Sensor “B” Circuit

What Does It Mean?

This is a generic powertrain diagnostic trouble code (DTC), meaning it covers all makes/models from 1996 onward. However, specific troubleshooting steps vary by vehicle.

The On-Board Diagnostic (OBD) trouble code P0486 is a generic code related to an issue in the Exhaust Gas Recirculation (EGR) valve electrical circuit “B”.

The purpose of the EGR valve is to introduce a regulated amount of exhaust gas into the intake manifold. The goal is to keep cylinder head temperatures below 2500 degrees F. Oxygen nitrates (Nox) form when temperatures exceed 2500 degrees F. Nox is responsible for smog and air pollution.

The control computer, either the Powertrain Control Module (PCM) or the Electronic Control Module (ECM), has detected an abnormally low, high, or non-existent signal voltage.
EGR Operating Principles

The P0486 trouble code refers to the same issue across all vehicles; however, there are many types of EGR systems, sensors, and activation methods. The only similarity is that they all vent exhaust gases into the intake manifold to cool cylinder head temperatures.

Introducing spent exhaust gases into the engine at the wrong time reduces power and causes rough idling or stalling. With this in mind, the computer programming only opens the EGR when engine speed is above 2000 RPM and closes it under load.

Symptoms

Symptoms depend on the position of the EGR pintle at the time of failure.

    The service engine soon light will illuminate, and the OBD code P0486 will be set. Additionally, a second code related to EGR sensor failure may be set. Code P0405 relates to low sensor voltage, and P0406 relates to a high voltage situation.
    If the EGR pintle is stuck partially open, the vehicle may not idle well or may stall.
    Knocking sounds may be heard under load or at high RPM.
    No symptoms at all.

Potential Causes

    Faulty EGR sensor “B”
    Defect in the sensor wiring harness.
    EGR pintle stuck in the closed position, with carbon buildup preventing it from opening.
    Lack of vacuum at the EGR solenoid.
    Faulty EGR solenoid.
    Defective EGR position sensor.
    Faulty EGR differential pressure feedback sensor.

Repair Procedures

All EGR valves have one thing in common: they recirculate exhaust from the exhaust system to the intake manifold. Beyond that, they differ in their methods of regulating the pintle opening and detecting its position.

The following repair procedures represent the most common issues responsible for the majority of EGR system failures. Wiring harness or sensor failures require a service manual to determine the proper wire identification and diagnostic procedures.

Keep in mind that wiring differs between manufacturers, and computers do not respond well if the wrong wire is probed. If you probe the wrong wire and send excessive voltage through the computer’s sensor input terminal, the computer may be fried.

At the same time, if the wrong connector is unplugged, the computer could lose its programming, requiring the vehicle to be restarted only after the dealer reprograms the computer.

    Code P0486 indicates a malfunction in circuit “B”, so check the EGR sensor connector for corrosion, bent or pushed terminals, or a loose connection. Clean any corrosion and reinstall the connector.
    Remove the electrical connector and take out the EGR valve. Check for carbon buildup in the EGR’s intake and exhaust passages. Clean any carbon deposits as needed so the pintle moves up and down smoothly.
    Check the vacuum line from the EGR to the solenoid and replace it if defects are found.
    Inspect the solenoid’s electrical connector for corrosion or defects.
    If the vehicle is a Ford, trace the two vacuum hoses from the EGR to the Differential Pressure Feedback EGR (DPFE) sensor at the rear of the manifold.
    Check for corrosion in both pressure hoses. Experience shows that these hoses can become clogged with exhaust carbon. Use a small pocket screwdriver or equivalent to clean the hoses of corrosion, and the sensor should resume functioning.

If the most common tests do not resolve the issue, a maintenance manual is needed to continue testing the wiring circuits. The best solution is to take the vehicle to a service center with the appropriate diagnostic equipment. They can quickly identify and repair this type of problem.

Related EGR Codes: P0400, P0401, P0402, P0403, P0404, P0405, P0406, P0407, P0408, P0409

P0487 EGR Control Circuit A Open

What Does This Code Mean?

The generic diagnostic code P0487, related to the powertrain/engine, primarily concerns diesel engines manufactured after 2004. It can affect various vehicle models, including those from Ford, Dodge, GM, Mercedes, Mitsubishi, Nissan, Suzuki, and Volkswagen.

The valve in question is located between the intake manifold and the air filter and operates similarly to a throttle body. Its role is to create a slight vacuum to draw exhaust gases into the intake manifold.

The Powertrain Control Module (PCM) controls the position of this Exhaust Gas Recirculation (EGR) control valve. Code P0487 is generated when the PCM detects an inconsistency in the voltage signals sent by the valve, indicating an electrical fault in the circuit.

Diagnostic procedures may vary depending on the manufacturer, the type of EGR valve used, and the wiring configuration.

Symptoms

Symptoms associated with engine code P0487 may include:

Illumination of the Malfunction Indicator Lamp (MIL) on the dashboard
Longer than normal post-treatment regeneration time (the exhaust system will take longer to reach the necessary temperature to burn soot deposits in the diesel particulate filter or catalyst)

Possible Causes

Among the most common causes for this code are:

Break in the signal circuit between the EGR control valve and the PCM
Short to voltage in the EGR valve signal circuit
Short to ground in the same circuit
Internal failure of the EGR control valve
PCM failure (although this is rare)

Diagnosis and Repairs

To begin, it is recommended to consult the technical service bulletins (TSBs) specific to your vehicle. Some known issues may already have manufacturer-proposed solutions, saving you time and money.

Here are the steps to follow:

Locate the EGR Control Valve: It is usually located between the intake manifold and the air filter, similar to a throttle body.
Visual Inspection: Carefully examine the connectors and wiring. Look for damaged, burned, melted, or corroded wires. Disconnect the connectors and check the condition of the metal terminals. Clean them if necessary with a specific electrical contact cleaner, then apply dielectric grease to prevent oxidation.
Clear the Codes: If you have a diagnostic tool, clear the code and check if it reappears. If it does not return, a connection issue was likely the cause of the error.
Electrical Tests:
- Disconnect the EGR control valve harness.
- With a digital multimeter (DVOM), measure the voltage on the signal circuit (red lead on the signal, black lead on a good ground).
- If no voltage (normally 5V) is present or if an abnormal voltage (e.g., 12V) is detected, the problem likely lies with the wiring or the PCM.
Ground Check:
- Use a test light connected to the positive terminal of the battery.
- Test the valve’s ground circuit.
- If the test light does not illuminate, the problem is related to the ground.
- If it lights up but flickers when you move the harness, this indicates a poor connection.
Valve Replacement:
If all tests are satisfactory and the P0487 code persists, the EGR control valve is likely defective. However, it is important not to completely rule out a PCM failure before replacing the valve.

P0488 EGR Throttle Position Control Performance Range

What does it mean?

This generic powertrain/engine diagnostic code generally applies to diesel engines built after 2004, including but not limited to certain Ford, Dodge, GM, Mercedes, Mitsubishi, Nissan, Suzuki, and VW vehicles.

This valve is located between the intake manifold and the air filter, similar to a throttle body. It is used to create a small vacuum that will draw exhaust gases into the intake manifold.

The Powertrain Control Module (PCM) tells the Exhaust Gas Recirculation (EGR) throttle control valve where to position itself. This code examines the voltage signals from the EGR throttle control valve to determine if they are correct based on PCM inputs. This code may have been set due to mechanical or electrical issues.

Troubleshooting steps may vary depending on the manufacturer, the type of EGR throttle control valve, and the wire colors.

Symptoms of a P0488 engine code may include:

Malfunction Indicator Lamp (MIL) illuminated
Active post-treatment regeneration time longer than normal (it will take more time for the exhaust system to heat up and burn off soot accumulated inside the diesel particulate filter/catalytic converter)

Possible causes for this code being set are:

Open in the signal circuit between the EGR throttle control valve and the PCM
Short to voltage in the signal circuit to the EGR throttle control valve
Short to ground in the signal circuit to the EGR throttle control valve
Faulty EGR throttle control valve – internally shorted
Failed PCM – unlikely

Diagnostic and Repair Procedures

A good starting point is always to check the Technical Service Bulletins (TSBs) for your specific vehicle. Your issue may be a known problem with a known fix released by the manufacturer and could save you time and money during diagnosis.

Next, locate the EGR throttle control valve on your specific vehicle. This valve is located between the intake manifold and the air filter, similar to a throttle body. Once located, visually inspect the connectors and wiring. Look for scratches, rubbing, exposed wires, burns, or melted plastic. Disconnect the connectors and carefully inspect the terminals (the metal parts) inside the connectors. Check if they appear burnt or have a greenish tint indicating corrosion. Use electrical contact cleaner and a plastic-bristled brush if terminal cleaning is necessary. Allow it to dry and apply dielectric silicone grease where the terminals make contact.

Scan Tool

If you have a scan tool, clear the diagnostic codes from the memory and see if this code returns. If it does not, the connections were likely your problem.

If the P0488 code returns, we will need to test the EGR throttle control valve and its associated circuits. Typically, there are 3 or 4 wires going to the EGR throttle control valve. Disconnect the harness going to the EGR throttle control valve. With a digital voltmeter (DVOM), test the signal circuit of the EGR throttle control valve (red lead to the valve’s signal circuit, black lead to a good ground). If there is no 5 volts at the valve, or if you see 12 volts at the valve, repair the wiring from the PCM to the valve, or possibly a faulty PCM.

If that checks out, ensure there is a good ground at the EGR throttle control valve. Connect a test light to the positive 12V battery terminal (red terminal) and touch the other end of the test light to the ground circuit going to the EGR throttle control valve circuit ground. If the test light does not illuminate, this would indicate a circuit problem. If it lights up, wiggle the wiring harness going to the EGR throttle control valve to see if the test light flickers, indicating an intermittent connection.

Conclusion

If all previous tests have passed and you continue to get a P0488, this would most likely indicate a faulty EGR throttle control valve, although a failed PCM cannot be ruled out until the EGR throttle control valve has been replaced.

P0489 Exhaust Gas Recirculation (EGR) “A” Control Circuit Low

Low Value of Exhaust Gas Recirculation Control Circuit “A”

What Does It Mean?

This is a generic powertrain code, meaning it covers all makes/models from 1996 onward. However, specific troubleshooting steps vary by vehicle.

These engine fault codes refer to a failure in the EGR (Exhaust Gas Recirculation) system. More specifically—the electrical aspect. The EGR is an integral part of the vehicle’s emission system, designed to prevent the formation of harmful NOx (nitrogen oxides) in the cylinders.

The EGR is operated by the engine management computer. The computer opens or closes the EGR based on load, speed, and temperature to maintain the correct cylinder head temperature. There are two wires to the electric solenoid on the EGR that the computer uses to activate it. A potentiometer is also located in the EGR solenoid, which signals the position of the EGR pintle (the control mechanism that opens and closes the passage).

It works somewhat like dimming your lights at home. When the switch is turned, the lights get brighter as you increase the voltage. Your engine computer sees no voltage change while it attempts to open or close the EGR, indicating it is stuck in one position. Code P0489 EGR Control Circuit “A” means no low voltage change indicates the EGR is opening or closing. P0490 is essentially the same but refers to a high circuit as opposed to low.

Unleaded fuel is prone to producing NOx under extreme temperatures in the engine cylinders. The EGR routes a regulated amount of exhaust gas to the intake manifold. The purpose is to sufficiently dilute the incoming fuel mixture to lower the cylinder head temperature below that at which NOx forms.

EGR operation is essential for more reasons than preventing NOx emissions—it allows for more advanced timing for greater power without knocking and a leaner fuel mixture for better fuel economy.

Symptoms

Symptoms vary depending on the pintle’s position in the EGR at the time of failure.

Extremely rough engine operation
Check engine light on
Decreased fuel economy
Loss of power
No start or very hard starting followed by rough idle

Potential Causes

Causes

of this DTC may include:

Short to ground
Short to battery voltage
Bad connector with pushed-back pins
Corrosion in the connector
Clogged EGR pintle
Failed EGR solenoid
Faulty EGR
Defective ECU or computer

Repair Procedures

If your vehicle has less than 100,000 miles, it is advisable to check your warranty. Most vehicles have an 80,000 or 100,000-mile warranty on emission controls. Second, go online and check relevant TSBs (Technical Service Bulletins) related to these codes and their repair.

To perform these diagnostic procedures, the following tools will be needed:

Volt/Ohmmeter
EGR wiring diagram
Jumper wire
Two paper clips or sewing needles

Open the hood and start the engine. If the engine is idling, pull the plug on the EGR. If the engine smooths out, the pintle is stuck in the EGR. Stop the engine and replace the EGR.

Look at the wire connector on the EGR. There are 5 wires; the two outer wires provide battery voltage and ground. The three central wires are the potentiometer used to signal the computer the amount of EGR flow. The center terminal is the 5-volt reference terminal.

Carefully inspect the connector for pushed-back pins, corrosion, or bent pins. Examine the wiring harness closely for missing insulation or possible shorts. Look for broken wires that could cause an open circuit.

With the voltmeter, probe one of the end terminals with the red wire and ground the black wire. Turn the key on and look for 12 volts at both terminals.
If no voltage is displayed, there is a broken wire between the EGR and the ignition bus. If 12 volts appears on only one side, the EGR has an internal open. Replace the EGR.
Remove the connector from the EGR and with the key on and engine off, probe the two outer terminals for power. Note which one has 12 volts and reinstall the connector.
Place a paper clip in the end terminal that had no power; this is the ground terminal. Attach the jumper wire to the paper clip. Ground the jumper. There will be an audible “click” as the EGR is activated. Disconnect the ground wire and start the engine. Ground the wire again, and this time the engine will start to run rough when the EGR is powered and smooth out when the ground is removed.
If the EGR clicked and made the engine run rough, the EGR is good; the problem is electrical. Otherwise, stop the engine and replace the EGR.
Probe the center terminal on the EGR connector. Turn the key. There should be 5.0 volts displayed if the computer is working correctly. Turn the key off.
Use the EGR wiring diagram and locate the “EGR Reference Voltage” terminal on the computer. Place a pin or paper clip in the computer connector at this point to probe the terminal again.
Turn the key. If 5 volts is present, the computer is good and the problem is in the EGR harness. If no voltage is present, the computer is faulty.

A tip for repairing the EGR circuit without replacing the computer: Look at the wiring diagram and locate the coolant temperature voltage reference terminal. Probe this terminal with the key on. If the 5-volt reference voltage is there, turn the key off and mark the two reference terminals used in these tests. Pull the computer connector, solder a jumper between these two terminals. Install the connector and the EGR will operate normally without replacing the computer.

P048A Exhaust Pressure Control Valve A Stuck Closed

What Does This Mean?

The P048A code is a generic OBD-II diagnostic trouble code related to the powertrain. It generally applies to modern vehicles equipped with onboard diagnostic systems, including those from brands like Ford, Dodge, Honda, Chevrolet, Volkswagen, etc. Although this code is generic, diagnostic and repair procedures can vary depending on the manufacturer, model, year, and engine configuration of the vehicle.

A P048A code means that the Powertrain Control Module (PCM) has detected a malfunction in the “A” Exhaust Backpressure Regulation Valve, often located on the cylinder number 1 side. In this case, the valve appears to be stuck in the closed position, preventing normal regulation of the exhaust flow.

What Is the Purpose of This Valve?

The Exhaust Backpressure Valve is designed to temporarily restrict the flow of exhaust gases, somewhat like a throttle valve, by partially closing the exhaust. This system is primarily used on turbocharged gasoline and diesel engines to:

Accelerate engine and coolant warm-up,
Improve heating performance, especially in cold climates.

It is electronically controlled by the PCM and is equipped with a position sensor to ensure precise control.

How Serious Is the P048A Code?

This code should be taken seriously. A stuck valve can affect:

The thermal comfort of the passenger compartment (heating),
Engine performance,
And in some cases, cause overheating.

Common Symptoms of the P048A Code:

Noticeable decrease in engine performance,
Engine or transmission overheating,
Very hot exhaust gases (sometimes glowing at the outlet),
Appearance of other codes related to exhaust pressure,
Malfunction Indicator Lamp (MIL) illuminated.

Possible Causes of the P048A Code:

Faulty valve position sensor,
Failed exhaust pressure sensor,
Stuck or malfunctioning regulation valve,
Damaged wiring, short circuit, or open circuit in the system.

Recommended Diagnostic Steps:

To properly diagnose this code, you will need:

An OBD-II scanner,
A digital multimeter (DVOM),
And ideally, an infrared thermometer.

Basic Procedure:

Visual inspection of the wiring and connectors associated with the valve.
Retrieve codes and data with the scanner, then clear the codes to see if P048A returns.
If air or coolant temperature codes are present, address them first.
Search for a Technical Service Bulletin (TSB) related to the vehicle and this code.
Test the voltage signals at the valve. If these are absent or abnormal, check the circuit continuity.
If the power supply is correct, test the valve itself: if it does not respond according to manufacturer specifications, replace it.
Also test related position or pressure sensors, if applicable.

An infrared thermometer can help determine if the valve is actually closed or open by observing temperature differences in the exhaust.

Additional Information:

The regulation valve is usually in the wide-open position when deactivated.
It often activates only during cold starts to speed up temperature rise.
A clogged catalytic converter or muffler can cause similar symptoms without necessarily generating a P048A code.
This system is common on supercharged or turbocharged engines.

P048B Exhaust Pressure Control Valve Circuit

What does it mean?

This generic powertrain diagnostic trouble code (DTC) generally applies to all OBD-II equipped vehicles with an exhaust pressure control valve sensor or switch. This may include, but is not limited to, vehicles from VW, Audi, Toyota, etc. Although generic, the exact repair steps may vary by make/model.

The Exhaust Pressure Control (EPC) valve is a solenoid valve used to regulate backpressure during cold weather. This allows for increased cabin heat, facilitates cold starting, and windshield defrosting.

In most cases, the Powertrain Control Module (PCM) uses information from the Exhaust Back Pressure (EBP) sensor, the Intake Air Temperature (IAT) sensor, and the Manifold Absolute Pressure (MAP) sensor to determine valve control. If the PCM detects a problem with the EPC or IAT, it will disable the ECP. Typically, the ECP is found on diesel engines.

Code P048B is set when the PCM detects a malfunction in the exhaust pressure control valve circuit.
How severe is this DTC?

The severity of this code is moderate to severe. It’s a good idea to address this code as soon as possible.

What are the symptoms of the code?

Symptoms of a P048B trouble code may include:

Check Engine Light
Increased emissions
Poor engine performance
Hard starting

What are some common causes of the code?

Causes

of this code may include:

Faulty exhaust pressure control valve
Wiring issues
Faulty PCM

What are the P048B troubleshooting steps?

Start by checking the exhaust pressure control valve and its corresponding wiring. Look for loose connections, damaged wiring, etc. If damage is detected, repair as necessary, clear the code, and see if it returns. Next, check for Technical Service Bulletins (TSBs) related to the issue. If nothing is found, you’ll need to proceed with step-by-step system diagnostics.

The following is a generalized procedure, as tests for this code vary by vehicle. To accurately test the system, you will need to refer to the manufacturer’s diagnostic flowchart.
Check the wiring

Before continuing, you’ll want to consult factory wiring diagrams to determine which wires are which. Autozone offers free online repair manuals for many vehicles and ALLDATA offers single-vehicle subscriptions.
Test the solenoid

Remove the solenoid connector. Use a digital multimeter set to ohms to check the solenoid’s internal resistance. To do this, connect the multimeter between the solenoid B+ terminal and the solenoid ground terminal. Compare the resistance measurement to factory repair specifications. If the meter displays a reading outside specifications or Out of Limits (OL) indicating an open circuit, the solenoid must be replaced.
Check the power side of the circuit

Ensure the vehicle has been sitting for at least a few hours (overnight is preferable) and is cold. Remove the solenoid connector. Ignition on, use a digital multimeter set to DC volts to check for solenoid power (typically 12 volts). To do this, connect the multimeter’s negative lead to ground and the multimeter’s positive lead to the solenoid B+ terminal on the harness side of the connector. If voltage is not present, connect the meter in ohms (ignition off) between the solenoid connector B+ terminal and the PCM’s solenoid supply voltage terminal. If the meter reads Out of Limits (OL), there is an open circuit between the PCM and the sensor that will need to be located and repaired. If the meter reads a numerical value, there is continuity.

If everything is okay so far, you’ll want to check that the PCM is powered. To do this, turn the ignition on and set the meter to DC volts. Connect the meter’s positive lead to the PCM’s EPC supply voltage terminal and the negative lead to ground. If there is no reference voltage from the PCM, the PCM is likely faulty. However, PCMs rarely fail, so it’s a good idea to recheck your work up to this point.
Check the ground side of the circuit

Ignition off, use a digital multimeter set to ohms to check for ground continuity. Remove the solenoid connector. Connect the multimeter between the solenoid ground terminal and chassis ground. If the meter reads a numerical value, there is continuity. If the meter reads Out of Limits (OL), there is an open circuit between the PCM and the solenoid that will need to be located and repaired.