P0454 Intermittent Evaporative Emission Control System Pressure Sensor

What does it mean?

This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles (Dodge, Ram, Ford, GMC, Chevrolet, VW, Audi, Toyota, etc.). Although generic, specific repair steps may vary by make/model.

When your OBD-II equipped vehicle stores a P0454 code, it means the Powertrain Control Module (PCM) has detected an intermittent signal from the Evaporative Emission System (EVAP) pressure sensor circuit.

To capture fuel vapors before they escape into the atmosphere, the EVAP system uses a vented storage tank (commonly called a canister) to store excess fuel vapors until the engine is operating under appropriate conditions to burn them efficiently.

Vapors from the fuel storage tank are evacuated through the pressure relief valve (atop the fuel tank). The pressure created when fuel is stored acts as a propellant and causes vapor evacuation through a network of metal tubes and rubber hoses; ultimately reaching the charcoal storage canister. The canister not only absorbs fuel vapors but also holds them for release at the appropriate time.

The typical EVAP system consists of a charcoal canister, EVAP pressure sensor, purge valve/solenoid, vent control valve/solenoid, and a complex system of metal tubes and rubber hoses extending from the fuel tank to the engine compartment.

The purge control valve/solenoid, which is the hub of the EVAP system, is electronically controlled by the PCM. The purge control valve/solenoid is used to regulate intake vacuum in the EVAP canister so fuel vapors are drawn into the engine when conditions are ideal for them to be burned as fuel instead of polluting the atmosphere.

EVAP pressure is monitored by the PCM using the EVAP pressure sensor. The EVAP pressure sensor can be difficult to access as it’s typically located atop the fuel tank and integrated into the fuel pump/fuel level sender unit housing. If the PCM detects that the EVAP system pressure signal is intermittent, a P0454 code will be stored and the Malfunction Indicator Lamp (MIL) may be illuminated.

Evaporative emission related trouble codes include P0450, P0451, P0452, P0453, P0455, P0456, P0457, P0458 and P0459.

Code Severity and Symptoms

Symptoms of this code may include:

In most cases, no symptoms will present with P0454
Slight decrease in fuel efficiency
MIL illumination (malfunction indicator lamp)

Causes

Possible causes for this code being set include:

Faulty EVAP pressure sensor
Clogged fuel tank pressure relief valve
Open or shorted wiring or connectors in EVAP pressure sensor circuit
Cracked or broken charcoal canister

Diagnostic and Repair Procedures

If I need to diagnose a P0454 code, I know I’ll need a diagnostic scanner, digital volt/ohmmeter, reliable vehicle information source like All Data DIY, and possibly even a smoke machine.

A visual inspection of EVAP system hoses, lines, wiring harnesses and connectors is a good place to begin your diagnosis. Pay particular attention to components routed near sharp edges or hot exhaust components. Remember to remove the fuel tank cap, inspect the seal, and reinstall it properly.

Next, I like to continue by connecting the scanner to the vehicle’s diagnostic port and retrieving all stored codes and freeze frame data. It’s a good idea to document this information as it can prove very helpful, especially if this is an intermittent code. After that, I like to clear the codes and test drive the vehicle until it enters OBD-II readiness mode or the code resets. EVAP codes typically require multiple drive cycles (with a failure in each) before being reset.

Observe the EVAP pressure sensor signal using the scanner’s diagnostic data stream. I know I’ve corrected the situation (by tightening or replacing the fuel cap) if system pressure meets manufacturer recommended specifications.

Before performing a smoke test, I would test the EVAP pressure sensor since this is an intermittent pressure sensor circuit code. The EVAP pressure sensor location can complicate testing as it’s typically located atop the fuel storage tank. After accessing the sensor, follow manufacturer recommendations for testing and replace the sensor if it doesn’t meet specifications.

Disconnect all associated controllers and test individual circuits with the DVOM if the EVAP pressure sensor meets manufacturer specifications. Repair or replace open or shorted circuits as necessary and retest the system.

Additional diagnostic notes:

Low or high EVAP pressure can result in P0454 storage
This code can be caused by electrical or mechanical malfunctions

P0455 Evaporative Emission Control System Leak Detected

What does it mean?

This diagnostic code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II. Although generic, specific repair steps may vary by make/model.

It indicates a fuel vapor leak or lack of purge flow in the EVAP control system. This means a significant leak has been detected.

The Evaporative Emission Control (EVAP) system prevents fuel vapors from escaping from a vehicle’s fuel system. Fuel vapors are routed through hoses to a charcoal canister for storage. Later, when the engine is running, a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.

Evaporative emission related fault codes include P0450, P0451, P0452, P0453, P0454, P0456, P0457, P0458, and P0459.

Symptoms

You will likely notice no driving issues.

Causes

A P0455 code most likely means one or more of the following has occurred:

A loose or improperly installed gas cap
A non-compliant gas cap (i.e., not a factory/original brand)
Other leak or damaged part in the EVAP system

Possible Solutions

With a P0455, the most common repair is to:

Remove and reinstall the gas cap, clear the codes, and drive for a day to see if the codes return.
If not, replace the gas cap and/or
Inspect the EVAP system for cuts/holes in the tubes/hoses (you may hear a vacuum noise or smell fuel), repair as necessary

Other EVAP DTCs: P0440 – P0441 – P0442 – P0443 – P0444 – P0445 – P0446 – P0447 – P0448 – P0449 – P0452 – P0453 – P0456

P0456 Evaporative Emission System – Small Leak Detected

What does it mean?

This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles. Although generic, specific repair steps may vary by make/model.

The Powertrain Control Module (PCM) performs various tests on the EVAP system at different times. Enhanced OBD II EVAP systems are designed to prevent fuel tank vapors from escaping into the atmosphere and instead purge them into the engine to be burned.

Regular pressure tests are performed by the PCM to monitor the sealed system for leaks. The PCM monitors the EVAP system pressure by observing the Fuel Tank Pressure (FTP) sensor. When the sensor indicates a small leak in the EVAP system, this code is set.

Evaporative emission related trouble codes include P0450, P0451, P0452, P0453, P0454, P0455, P0457, P0458, and P0459.

Symptoms

potential

There will likely be no noticeable symptoms other than the Malfunction Indicator Lamp (MIL). This is because the EVAP system is a closed system and only controls fuel tank vapors, not engine management.

Causes

Usually, this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running could also trigger this code, or if the cap was not properly tightened. One of the following could also be the cause:

A small leak in one of the EVAP hoses or fuel tank lines
A small leak in the purge valve or vent valve
The EVAP canister has a small leak

Possible Solutions

First, using a scan tool, activate the vent solenoid, sealing the system. Then monitor the Fuel Tank Pressure (FTP) sensor. If the system seals properly, the reading will remain constant. If not, the pressure sensor will show this. If the system is leaking slowly, use a smoke machine and watch for smoke escaping from the system at an EVAP component. Anywhere smoke is escaping from the system indicates the faulty component. Do not pressurize the EVAP system with air. This could damage the system’s purge and vent solenoids.

Other EVAP DTCs: P0440 – P0441 – P0442 – P0443 – P0444 – P0445 – P0446 – P0447 – P0448 – P0449 – P0452 – P0453 – P0455

P0457 Evaporative Emission Control System Leak Detected

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.

Diagnostic Trouble Code (DTC) P0457 relates to a vacuum leak in the Evaporative Emission system used to prevent fuel vapor leaks into the atmosphere. P0456 and P0455 are similar codes referring to the degree of vacuum leak from smallest to largest. The fix is similar in all cases.
This code does not cause driveability issues but should be fixed as soon as possible. It indicates a vacuum leak is present that compromises the operation of the Evaporative Emission system.

Automobiles require two types of emission controls – passive and active. The active part involves controlling the fuel ratio and the catalytic converter’s ability to convert carbon monoxide, nitrogen oxides, and hydrocarbons into harmless water and carbon dioxide.

The passive part relates to this P0457 code. Fuel vapor accounts for 20% of harmful evaporative emissions. To prevent these vapors from entering the atmosphere, they are contained in the fuel system and drawn into the engine via the intake manifold.

The Evaporative Emission system consists of the fuel tank, a vent line to the charcoal canister to contain fuel vapors, a pressure sensor on the fuel tank, a purge valve on the charcoal canister, a vent line to the fill neck shut-off valve, and a purge line from the charcoal canister purge valve to the intake manifold.

When the engine is off, the vent shut-off valve and the tank purge valve are closed. Fuel cannot escape into the atmosphere. When the engine starts, the purge valve on the tank opens to allow trapped fuel vapor to be drawn by engine vacuum into the intake manifold. At the same time, the vent shut-off valve also opens to allow a small amount of air into the tank to mix with the fuel vapor for a better mixture. Once purged and the pressure sensor in the tank shows a significant drop, both valves close again, sealing the system.

There is a major leak preventing the system from being drawn into the vacuum needed to pull fuel vapors into the engine to burn.

Related Evaporative Emission fault codes include P0450, P0451, P0452, P0453, P0454, P0455, P0456, P0458, and P0459.

Symptoms

Symptoms of a P0457 code vary depending on the component or system causing the fuel seal disruption. Not all will be present at once.

    Illumination of the Malfunction Indicator Lamp (MIL) with P0457 DTC set
    There may be an occasional fuel smell
    Fuel economy is affected when fuel can evaporate into the atmosphere

Potential Causes

Causes

of this DTC may include:

    This code relates to a major leak. The most common cause is the gas cap. Either it was left loose, or it is cracked, missing, or has a foreign object or dirt on the threads preventing a proper seal.
    If the gas cap is not the cause, a hose may have rotted and cracked or perhaps come loose. The system is not under any abuse, so age and weather conditions may be to blame.
    The vacuum canister may have cracked

Diagnostic and Repair Procedures

Always go online and check for any TSBs (Technical Service Bulletins) related to your vehicle and this code.

The emission system on most vehicles is covered by warranty for an extended period, 80 to 100,000 miles. The reasoning relates to the fact that without causing driveability issues, many owners will neglect to repair such a problem.

    Inspect the gas cap. Look for dirt on the threads, cracks, and general condition. Install it and ensure it clicks into place. If the gas cap was to blame, the Check Engine Light may be reset with a simple code scanner, or the code will reset after three drive cycles where the computer no longer sees the issue.
    Raise the vehicle and inspect all vacuum hoses. Replace any that are cracked or have lost flexibility and will no longer create a tight fit on the port.
    Check the fitting on the intake manifold for cracks at the point where the emission hose connects.
    Check the charcoal canister for cracks.
    Place a vacuum pump on the emission hose (engine side) and pump to about 10 inches of vacuum. If there is no leak, the vacuum will hold its position. If it drops, a leak is present between the engine and the canister purge valve.

P0458 Low Purge Control Valve Circuit System Evaporative Emission

What does it mean?

On vehicles equipped with Evaporative Emission Control (EVAP) systems, the engine draws excess fuel vapors from the gas tank that would otherwise be released into the atmosphere. The purpose of the system is to reduce vehicle emissions.

The evaporative emission system consists of the fuel tank, a vent line to the charcoal canister to contain fuel vapors, a pressure sensor on the fuel tank, a purge valve on the charcoal canister, a vent line to the fill neck shut-off valve, and a vent line from the charcoal canister purge valve to the intake manifold. When the engine is off, the vent shut-off valve and the tank purge valve are closed.

Fuel cannot escape into the atmosphere. When the engine starts, the purge valve on the tank opens to allow trapped fuel vapor to be drawn by engine vacuum into the intake manifold. At the same time, the vent shut-off valve also opens to allow a small amount of air to enter the tank and mix with the fuel vapor for better combustion. Once purged and the pressure sensor in the tank shows a significant drop, both valves close again, sealing the system.

The fuel vapor is routed via a vacuum line to the engine intake, and the purge valve/solenoid measures the desired amount of fuel vapors, controlled by the Powertrain Control Module (PCM) or Engine Control Module (ECM). The PCM/ECM monitors the voltage to the purge control valve and detected a voltage lower than expected.

Related purge control valve circuit codes include:

P0443 Evaporative Emission Control System Purge Control Valve Circuit
P0444 Evaporative Emission Control System Purge Control Valve Circuit Open
P0445 Evaporative Emission Control System Purge Control Valve Circuit Shorted
P0459 Evaporative Emission System Purge Control Valve Circuit High

Symptoms

Visible symptoms of a P0458 EVAP trouble code typically include only the illumination of the Malfunction Indicator Lamp (MIL) or the “Check Engine/Service Engine Soon” light. Other trouble codes may accompany this code. In some cases, there may be a gas smell and/or a slight decrease in fuel efficiency.
Potential causes

Causes

of this DTC may include:

Faulty fuse or relay
Defective purge control valve
Faulty EVAP purge solenoid control
Open or shorted engine wiring harness or connector
Open or shorted purge control solenoid
PCM/ECM malfunction

Diagnosis and Repair

A good first step if you receive a P0458 is to check for Technical Service Bulletins (TSBs) that apply to your vehicle’s year/make/model. If it is a known issue, a TSB can save time and money during diagnosis and repair.

Visually inspect the engine wiring harness connectors for any damage, look for pinched wires, loose or bent pins, or bare wiring without insulation. Typically, the purge control valve is powered by the battery and triggered on and off with a duty cycle via the PCM/ECM. Using the manufacturer’s wiring diagrams, identify the type of circuit used and check for battery voltage with the key on/engine off on the power side of the control solenoid connector using a Digital Volt-Ohm Meter (DVOM) set to the volts scale. If no battery voltage is present, trace the wiring to determine the cause.

Check for a short to ground by disconnecting the harness from the control valve solenoid and the voltage source. Using the DVOM set to the ohms scale, with the negative lead connected to a known good ground and the positive lead to each end that powers the control valve solenoid. If resistance is very low, suspect a short to ground and repair the wiring harness. Check for a short to ground on the control side of the harness by disconnecting the harness from the control valve solenoid and the PCM/ECM harness. Identify the correct wire and using the DVOM set to an ohms scale, check resistance with the negative lead connected to a known good ground and the positive lead on one of the control circuit wire bundles. If resistance is very low, suspect a short to ground and repair the wiring harness.

Purge Control Solenoid – Check continuity at the purge control solenoid connector pins after removing the plug from the harness using the DVOM set to the ohms scale. Verify that resistance meets manufacturer specifications. Check for a short to ground using the DVOM with the negative lead attached to a known good ground and the positive lead on each of the control valve solenoid terminal pins. Resistance should be very high or above the limit (OL). If very low resistance is detected, suspect the control valve solenoid is shorted to ground and replace it with a known good unit.

Since the EVAP system only activates under certain driving conditions, it will be necessary to monitor EVAP control operation using a capable advanced scan tool and perform a road test under the required driving conditions to activate the EVAP system. Some

P0459 High Value in Evaporative Emission System Purge Control Valve Circuit

What does it mean?

The evaporative emission system consists of the fuel tank, a vapor line to the charcoal canister to contain fuel vapors, a pressure sensor on the fuel tank, a purge valve on the charcoal canister, a vapor line to the fill neck shut-off valve, and a vapor line from the charcoal canister purge valve to the intake manifold. When the engine is off, the vent shut-off valve and the tank purge valve are closed.

Fuel cannot escape into the atmosphere. When the engine starts, the purge valve on the tank opens to allow the trapped fuel vapor to be drawn by engine vacuum into the intake manifold. At the same time, the vent shut-off valve also opens to allow a small amount of air to enter the tank and mix with the fuel vapor for a better mixture. Once purged and the pressure sensor in the tank shows a significant drop, both valves close again, sealing the system.

Related purge control valve circuit codes include:

P0443 Evaporative Emission Control System Purge Control Valve Circuit
P0444 Evaporative Emission Control System Purge Control Valve Circuit Open
P0445 Evaporative Emission Control System Purge Control Valve Circuit Shorted
P0458 Evaporative Emission System Purge Control Valve Circuit Low

Symptoms

Visible symptoms of a P0459 EVAP trouble code typically include only the illumination of the Malfunction Indicator Lamp (MIL) or the “Check Engine/Service Engine Soon” light. Other trouble codes may accompany this code. In some cases, there may be a gas smell and/or a slight decrease in fuel efficiency.

Potential Causes

Causes

of this DTC may include:

Blown fuse or relay
Faulty purge control valve
Faulty EVAP purge solenoid control
Electrical wiring issue in the engine wiring harness or connector
Electrical circuit problem in the purge control solenoid
PCM/ECM malfunction

Diagnosis and Repair

A good first step if you receive a P0459 is to check for Technical Service Bulletins (TSBs) that apply to your vehicle’s year/make/model. If it is a known issue, a TSB can save you time and money during diagnosis and repair.

Check for a short to ground by disconnecting the harness at the control valve solenoid and the voltage source. Using the DVOM set to the ohms scale, with the negative lead connected to a known good ground and the positive lead to each end that powers the control valve solenoid. If the resistance is very low, suspect a short to ground and repair the wiring harness. Check for a short to ground on the control side of the harness by disconnecting the harness from the control valve solenoid and the PCM/ECM harness. Identify the correct wire and using the DVOM set to an ohms scale, check the resistance with the negative lead connected to a known good ground and the positive lead on one of the control circuit wire harnesses. If the resistance is very low, suspect a short to ground and repair the wiring harness.

Purge Control Solenoid – Check for continuity at the purge control solenoid connector pins after removing the plug from the harness using the DVOM set to the ohms scale. Verify that the resistance meets the manufacturer’s specifications. Check for a short to ground using the DVOM with the negative lead attached to a known good ground and the positive lead on each of the control valve solenoid terminal pins. The resistance should be very high or above the limit (OL). If very low resistance is detected, suspect that the control valve solenoid is shorted to ground and replace it with a known good unit.

Since the EVAP system only activates under certain driving conditions, it will be necessary to monitor the EVAP control operation using a capable advanced scan tool and perform a road test under the required driving conditions to activate the EVAP system. Some advanced scan tools have an internal test to manually activate the EVAP system. Verify that the PCM/ECM is commanding the EVAP system. If the system is operating correctly, it will be necessary to probe the PCM/ECM wiring harness connector using a graphing multimeter or an oscilloscope with a duty cycle function, with the positive lead on the purge control valve pin and the negative lead connected to a known good ground source. The duty cycle should match what is commanded by the PCM/ECM during EVAP operation. If no duty cycle is present, the PCM/ECM may be faulty.

P045A exhaust gas recirculation B control circuit

What does it mean?

This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles with an exhaust gas recirculation system. Vehicle makes may include (but are not limited to) Land Rover, GMC, Chevrolet, Dodge, Chrysler, Ford, Toyota, Honda, etc. Although generic, specific repair steps may vary by make/model.

The exhaust gas recirculation (EGR) system is controlled by a vacuum solenoid. The solenoid is supplied with ignition voltage. The powertrain control module (PCM) controls the vacuum solenoid by grounding the control circuit (ground) or driver.

The main function of the driver is to provide ground to the controlled component. Each driver has a fault circuit that the PCM monitors. When the PCM powers a component, the control circuit voltage is low or near zero. When the component is off, the voltage on the control circuit is high or near battery voltage. The PCM monitors these conditions and if it does not see the appropriate voltage at the right time, this code is set.

The EGR system is used on engines to reduce combustion temperature, which in turn reduces emissions. Refer to a vehicle-specific repair manual to determine what the EGR circuit “B” is in your particular case.

Potential Symptoms

Usually, a fault in the control circuit will leave no noticeable symptoms other than the malfunction indicator lamp (MIL) illuminating. However, if the EGR control solenoid is stuck due to debris, etc., the code may be accompanied by misfires during acceleration, rough idle, or a stalling engine.

Causes

of an EGR P045A code may include:

Faulty EGR solenoid
Excessive resistance in the control circuit (PCM controlled ground) due to an open, chafing, or damage to the harness
Poor connection to the EGR solenoid harness (worn or loose pins)
Water intrusion at the EGR solenoid harness
Blockage in the EGR control solenoid holding or closing the solenoid causing excessive resistance
Loss of EGR solenoid supply voltage
Faulty PCM

Possible Solutions

If you encounter this fault code, we encourage you to refer to a vehicle-specific repair guide for your particular year, make, model, and engine. The following information is more general in nature. Also, be sure to check for TSBs (technical service bulletins) that may apply to your vehicle.

With the ignition on and engine off, use a scan tool to activate the EGR solenoid. Listen or feel for a click, indicating the solenoid is operating.

If the solenoid operates, you will need to check the current draw on the ground circuit. It should be less than one amp. If it is, the problem is intermittent. If not, there is excessive resistance in the circuit and perform the following:

1. When activated, see if you can blow lightly through it. If you cannot, there may be a blockage causing excessive resistance. Replace the EGR solenoid as needed. If there is no blockage, disconnect the EGR solenoid and the PCM connector containing the EGR solenoid control circuit. Using a digital volt-ohmmeter (DVOM), check the resistance between the control circuit and battery ground. This should be infinite. If not, there is a short to ground in the control circuit. Repair the short to ground and retest as needed.

2. If the solenoid does not click as it should, disconnect the EGR solenoid connector and connect a test light between the two wires. Using the scan tool, activate the EGR solenoid. The light should come on. If it does, replace the EGR solenoid. If it does not, perform the following: a. Check for 12 volts on the solenoid ignition supply voltage. If not present, inspect the supply circuit for an open or short due to chafing or breakage and retest. b. If it still does not work: manually ground the EGR solenoid control circuit. The light should come on. If it does, repair the open EGR solenoid control circuit and retest. If not, replace the EGR solenoid.

P045B Exhaust Gas Recirculation Control Circuit B

What does it mean?

This diagnostic code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles with an exhaust gas recirculation system. Vehicle makes may include (but are not limited to) Land Rover, GMC, Chevrolet, Dodge, Chrysler, Ford, Toyota, Honda, etc. Although generic, specific repair steps may vary by make/model.

The purpose of the EGR (Exhaust Gas Recirculation) system is to redirect exhaust gases to the cylinders. Since exhaust gases are inert, they displace oxygen and fuel, thereby reducing cylinder temperatures, which in turn reduces nitrogen oxide emissions. For this reason, it must be carefully metered into the cylinders (via the EGR valve) so as not to harm engine performance. (Too much EGR and the engine won’t idle).

If you have a P045B, the EGR valve is likely an electrically controlled EGR valve instead of a vacuum-operated EGR valve. Additionally, the valve usually features a feedback system that informs the PCM (Powertrain Control Module) of the valve’s position; open, closed, or somewhere in between. The PCM needs to know this to determine whether the valve is operating as required. If the PCM determines that the valve should operate, but the feedback circuit shows that the valve is not open, this code will be set. Or if the PCM determines that the valve should be closed but the feedback signal indicates that the valve is open, this code will be set.

Refer to a vehicle-specific repair manual to determine what the “B” EGR circuit is in your particular case.

Potential Symptoms

There may be no symptoms of a P045B trouble code other than the MIL (Malfunction Indicator Lamp) or check engine light.

However, exhaust gas recirculation systems are inherently problematic due to carbon buildup in the intake manifold, etc. This normal buildup can lodge in an EGR valve, holding it open when it should be closed. If this is the case, the engine may idle roughly or not at all. If the valve is faulty and does NOT open, the symptoms would be higher combustion temperatures and consequently higher NOx emissions. But these latter symptoms will not be visible to a driver.

Causes

Usually, this code indicates carbon buildup or a faulty EGR valve. However, it does not rule out the following:

Open or short circuit in the 5-volt reference circuit
Open or short circuit in the ground circuit
Open or short circuit in the PCM-controlled voltage circuit
Faulty PCM (less likely)

Possible Solutions

If you encounter this trouble code, we encourage you to refer to a vehicle-specific repair guide for your particular year, make, model, and engine. The following information is more general in nature. Also, be sure to check for TSBs (Technical Service Bulletins) that may apply to your vehicle.

Using a scan tool, the “B” EGR valve should open when looking at the actual EGR position (it will likely be labeled “Desired EGR” or something similar). The actual EGR position should be very close to the “Desired” EGR position. If it is, the problem is likely intermittent. It could be a piece of deposited carbon that has since dislodged, or it could be a faulty EGR valve winding that opens or shorts intermittently when the valve temperature changes.
If the “Desired” EGR position is not close to the “Actual” position, unplug the EGR sensor. Check for a proper 5-volt reference voltage at the connector. If it does not show reference voltage, repair an open or short circuit in the 5-volt reference circuit.
If there is a 5-volt reference voltage, activate the EGR with the scanner, monitor the EGR ground circuit with a DVOM (Digital Volt/Ohm Meter). It should indicate a good ground. If not, repair the ground circuit.
If there is a good ground, check the control circuit. It should indicate a voltage that varies depending on the EGR opening percentage. As it opens more, the voltage should increase accordingly. If it does, replace the EGR valve.
If the voltage does not increase incrementally, repair the open or short circuit in the EGR control circuit.

P045C Low B Exhaust Gas Recirculation Control Circuit

What does it mean?

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, whose function is to prevent the formation of harmful NOx (nitrogen oxides) in the cylinders.

The EGR is actuated by the engine management ECU. The ECU 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 which the ECU uses to activate it. A potentiometer is also located in the EGR solenoid that 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 ECU sees no voltage change while it attempts to open or close the EGR, indicating it is stuck in one position. Code P045C EGR Control Circuit “B” means no low voltage change to indicate the EGR opening or closing. P045D is basically the same but it means high circuit as opposed to low. Refer to a vehicle-specific repair manual to determine which is the EGR “B” circuit in your particular case.

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 just preventing NOx emissions – it allows for more advanced timing for more power without detonation, and a leaner fuel mixture for better fuel economy.

Symptoms

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

Extremely rough running engine
Check Engine Light illuminated
Decreased fuel economy
Loss of power
No start or very hard starting followed by rough idle

Potential Causes

Causes

of this DTC can 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 PCM

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. Secondly, go online and check for relevant TSBs (Technical Service Bulletins) related to these codes and their repair.

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

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

Open the hood and start the engine. If the engine is idling roughly, 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 “B”. There are 5 wires; the two outer wires provide battery voltage and ground. The three center wires are the potentiometer used to signal the ECU 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. Carefully examine the wiring harness for missing insulation or potential shorts. Look for broken wires that could cause an open circuit.

With the voltmeter, probe one of the end terminals with the red lead and ground the black lead. Turn the key on and look for 12 volts on both terminals.
If no voltage is displayed, there is a broken wire between the EGR and the ignition bus. If 12 volts displays 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. Make a note of which one has 12 volts and reinstall the connector.
Place a paper clip into the end terminal that did not have power; this is the ground terminal. Attach the jumper wire to the paper clip. Ground the jumper wire. 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 will 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 on. There should be 5.0 volts displayed from the ECU, so it is working correctly. Turn the key off.
Use the EGR wiring diagram and locate the “EGR Reference Voltage” terminal on the ECU. Place a pin or paper clip into the ECU connector at this point to back-probe the terminal.
Turn the key on. If 5 volts is present, the ECU is good and the problem is in the EGR harness. If no voltage is present, the ECU is faulty.

A tip for repairing the EGR circuit without replacing the ECU: Look at the wiring diagram and locate the Coolant Temperature Sensor reference voltage 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 ECU connector, solder a jumper wire between these two terminals. Install the connector and the EGR will function normally without replacing the ECU.

P045D High Exhaust Gas Recirculation B Control Circuit

What does it mean?

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 whose function is to prevent the formation of harmful NOx (nitrogen oxides) in the cylinders.

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 ECU sees no voltage change while it is attempting to open or close the EGR, indicating it is stuck in one position. Code P045D “EGR Control Circuit ‘B'” means no high voltage change to indicate the EGR is opening or closing. P045C is basically the same but it means the circuit is low as opposed to high. Refer to a vehicle-specific repair manual to determine which is the EGR ‘B’ circuit in your particular case.

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

Extremely rough running engine
Check Engine Light illuminated
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 PCM or ECU

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. Secondly, go online and check for relevant TSBs (Technical Service Bulletins) related to these codes and their repair.

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

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

Open the hood and start the engine. If the engine is idling roughly, 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 ‘B’. There are 5 wires; the two outer wires provide battery voltage and ground. The three center wires are the potentiometer used to signal the ECU 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. Carefully examine the wiring harness for any missing insulation or potential shorts. Look for broken wires that could cause an open circuit.

Use the EGR wiring diagram and locate the “EGR Reference Voltage” terminal on the ECU. Place a pin or paper clip into the ECU connector at this point to back-probe the terminal.
Turn the key on. If 5 volts is present, the ECU is good and the problem is in the EGR harness. If no voltage is present, the ECU is faulty.