P047F Exhaust Pressure Control Valve A Stuck Open

What does it mean?

This is a generic powertrain diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles. This may include, but is not limited to, Dodge, Honda, Chevy, Ford, VW vehicles, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

A stored P047F code means that the Powertrain Control Module (PCM) has detected a malfunction in one of the exhaust pressure control valves (regulator). The “A” valve typically indicates that the issue occurred in the engine bank containing cylinder number 1, but designs vary by manufacturer. In this case, the valve appears to be stuck in the open position.

Exhaust pressure regulators (also called back-pressure) are used in turbocharged gasoline and diesel engines. The operation of the exhaust back-pressure control valve is often similar to that of a throttle body. It uses an electronically controlled plate to restrict exhaust flow as determined by the PCM. There is also an exhaust back-pressure control valve position sensor and/or an exhaust back-pressure sensor.

Increased exhaust back-pressure is used to raise engine and coolant temperature more quickly. This can be particularly useful in very cold climates.

This is a basic generic overview of how the exhaust pressure group valve operates. Check the specifications of the vehicle in question before making assumptions. When the PCM detects a cold air intake temperature below a minimum threshold, it initiates the operation of the exhaust back-pressure valve and maintains it until the intake air temperature normalizes. Activation of the exhaust back-pressure regulator typically only occurs once per ignition cycle. The exhaust back-pressure control valve is designed to park in the wide-open position once it is deactivated by the PCM.

If the PCM detects that the exhaust back-pressure regulator is not in the desired position, or if the exhaust back-pressure sensor indicates it is out of position, a P047F code will be stored and a Malfunction Indicator Lamp (MIL) may illuminate.
How severe is this DTC?

Since exhaust back-pressure can affect climate control and driving functions, a stored P047F code should be addressed with some urgency.
What are some of the symptoms of the code?

Symptoms of a P047F trouble code may include:

Delayed engine warm-up
Engine stalling or stumbling when cold
Reduced engine performance when cold
Other exhaust back-pressure codes

What are some common causes of the code?

Causes

of this P047F code may include:

Faulty exhaust back-pressure control valve position sensor
Bad exhaust pressure sensor
Defective exhaust pressure control valve
Open or shorted wiring in any of the exhaust pressure control valve circuits

What are the troubleshooting steps for P047F?

A reliable source of vehicle information will be needed to diagnose a P047F code. Other necessary tools:

A diagnostic scanner
A digital volt/ohmmeter (DVOM)
An infrared thermometer with a laser pointer

After a careful visual inspection of the wiring and connectors related to the system, locate the vehicle’s diagnostic port. Connect the scanner to the port and retrieve all stored codes and freeze frame data. Note this information, as it may be useful during your diagnosis.

Now, clear the codes and test-drive the vehicle to see if the P047F returns immediately. If there are intake air temperature codes or engine coolant temperature codes, diagnose and repair them before attempting to diagnose the P047F.

Look for Technical Service Bulletins (TSBs) that apply to the vehicle, the codes, and the symptoms in question. If you find one that matches, it will likely help you greatly in your diagnosis.

If no obvious wiring or connector issues are found, start by testing the expected voltage signal at the exhaust pressure control valve (using the DVOM). You may need to use the scanner to simulate a cold start condition and activate the exhaust pressure control system.
If the proper voltage/ground signal is not detected at the exhaust pressure control valve connector, disconnect all associated controllers and use the DVOM to test the resistance and continuity of the individual circuit. Circuits found to be out of specification must be repaired or replaced.
If the correct voltage/ground level is found at the exhaust pressure control valve, follow the manufacturer’s recommendations for testing the exhaust pressure control valve (using the DVOM). If the exhaust pressure control valve pinout test does not match the manufacturer’s specifications, it must be replaced.
If the exhaust pressure control valve and circuits are functioning, test the exhaust pressure control valve position sensor or the exhaust pressure sensor (as applicable) according to the manufacturer’s specifications. Replace faulty components as necessary.

You can use the infrared thermometer to take a reading of the actual exhaust temperature if no scanner data display is available. This could prove useful in determining whether the exhaust pressure control valve is actually operating or not. It can also detect a valve stuck in the open or closed position.

A faulty catalytic converter or muffler will not cause a P047F code to be stored
Exhaust pressure control systems are most commonly used in turbocharged/supercharged applications

P0480 Cooling Fan Relay 1 Control Circuit

Error code P0480 means there is a problem with your vehicle’s engine cooling fan control circuit. In other words, your car’s computer (the PCM) is trying to turn on the cooling fan, but there is an issue preventing it from working correctly.

Here is a simpler explanation:

The cooling fan is important for preventing your engine from overheating, especially when the car is idling or moving slowly and air is not flowing well through the radiator.
The car’s computer (PCM) monitors the engine temperature. When it gets too hot, it sends a signal to turn on the fan.
The P0480 code appears when the computer tries to turn on the fan but does not receive confirmation that the fan is operating.

In summary, code P0480 indicates a problem in the electrical circuit that controls your engine’s cooling fan. This could be due to a faulty relay, a wiring issue, a blown fuse, the fan itself being broken, or even a problem with the temperature sensor or the car’s computer (although this is less common).

It is important to fix this issue quickly, as a cooling fan that is not working can lead to engine overheating, which can cause expensive damage.

P0481 Cooling Fan Relay 2 Control 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.

If your vehicle’s check engine light comes on and after retrieving the code you find P0481 displayed, it refers to the engine cooling fan circuit. This is a generic code applying to all OBD-II vehicles.

While driving, sufficient air passes through the radiator to effectively cool the engine. When you stop the car, no air flows through the radiator and the engine temperature begins to rise.

The PCM detects the engine temperature increase via the Coolant Temperature Sensor located near the thermostat. When the temperature reaches approximately 223°F (the exact value depends on make/model/engine), the PCM commands the cooling fan relay to activate the fan by providing ground to the relay.

There’s a problem in this circuit causing the fan not to operate, allowing the engine to overheat when stationary or at low speeds. When the PCM attempts to activate the fan and detects that the command and result don’t match, the code is set.

NOTE: P0481 refers to the primary circuit, while P0480 and P0482 relate to the same issue but concern different fan speed relays.

Symptoms

Symptoms may include:

Check engine light illumination with P0481 code stored
Engine temperature rising when vehicle is stopped and idling

Potential Causes

Causes of this DTC may include:

Faulty cooling fan control relay 2
Open or shorted cooling fan control relay harness
Poor electrical connections in the circuit
Faulty cooling fan 2
Defective coolant temperature sensor
Open or shorted cooling fan harness
Poor electrical connection in 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’s always wise to consult Technical Service Bulletins for your specific vehicle to see what types of complaints have been submitted regarding this code. Search using your preferred search engine for “technical service bulletins for…” Look for the code and manufacturer-recommended repair type. This is also good practice before purchasing a vehicle.

Many vehicles have two engine fans – one for engine cooling and a second for A/C condenser cooling and additional engine cooling.

The fan not in front of the A/C condenser is the primary cooling fan and should be the initial focus. 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. Check the fan and ensure there are no obstructions in front of the radiator blocking airflow. Spin the fan with your finger (ensure vehicle and ignition are off). If it doesn’t 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’re good, remove the cooling fan relays. The underside of the fuse box cover usually indicates locations, otherwise check the owner’s manual.

The vehicle PCM’s function is to act as ground for operating components, not to provide power. Fan relays are essentially remote light switches. The fan and other devices draw too much amperage to be safely located in the cockpit, so they’re kept under the hood.

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

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

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

If the fan operated, check the relays. Look at the side of the relay for the switched power terminal or simply turn the key. Check terminals for additional power supply and identify their locations on the relay.

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

If the circuit didn’t close or the relay didn’t click, the relay is bad. Check all relays similarly to ensure they all function.

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

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

The reading will be approximately 2.5. For accurate readings, consult a service manual. Precision isn’t necessary as all sensors may differ – you just want to know if it’s working. Reconnect it and warm up the engine.

Stop the engine and pull the CTS plug again. Check it with the ohmmeter – there should be a significant resistance change, otherwise the sensor is bad.

If the above procedure didn’t find a failure, the likely cause is either a poor connection to the PCM or the PCM itself. Don’t proceed further without consulting your service manual. Disconnecting the PCM can cause programming loss and the vehicle may not start unless towed to the dealer for reprogramming.

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.