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.
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.