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Error Code P045C is defined as Exhaust Gas Recirculation B Control Circuit Low. This code refers to a problem in the EGR, to be more specific, it’s an electrical issue.
This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II, especially those made from 1996 up to the present day. These vehicles may include (but are not limited to) Vehicle brands may include (but are not limited to) Land Rover, GMC, Chevrolet, Dodge, Chrysler, Ford, Toyota, Honda, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.
The EGR system is controlled by the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes), by opening or closing the EGR as load, speed, and temperature dictate to keep the right temperature for the cylinder head. The EGR has two wires to the electrical solenoid, which the computer activates. There’s also a potentiometer located in the EGR solenoid that tells the position of the EGR’s pintle (the operating mechanism that opens and closes the passage).
This potentiometer works like dimming your lights at home; when the switch is on, the light gets brighter as you increase the voltage. The PCM fails to see any voltage change as it attempts to open or close the EGR indicating it is stuck in one position. Error Codes P045C means there is no low voltage change to indicate the EGR is opening or closing. It’s similar to Error Code P045D, but P045D means circuit high rather than low.
As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Drivability and performance symptoms usually vary depending on the position of the pintle in the EGR when the error occurred. Common symptoms include:
- Extremely rough running engine
- Increase in fuel consumption
- Decrease in power
- No start or very difficult to start followed by rough idle
Common causes for this code include:
- Short to ground
- Short to battery voltage
- Damaged connector (pushed out pins)
- Corrosion in the connector
- Damaged EGR pintle
- Defective EGR solenoid
- Bad EGR
- Bad PCM (rare)
How to Check
To diagnose for this code, open the hood of your vehicle and then start the engine. If you hear rough idle, pull the plug on the EGR. If the idle of the engine smooths out, then the pintle is stuck in the EGR. Shut the engine off and replace the EGR.
Test the wire connector on the “B” EGR. There will be 5 wires. The two outside wires supply battery voltage and the ground. The three wires in the middle are called the potentiometer. They work by sending signals to the PCM as to the amount of EGR flow. The terminal in the middle is the 5-volt reference terminal.
Check the connector thoroughly for pushed out pins, corrosion or bent pins. Look closely at the wiring harness for any missing insulation or possible shorts. Look for broken wires that could cause an open circuit.
Using the voltmeter, probe either end terminal with the red lead and ground the black lead. Turn the key on and look for 12-volts and both end-terminals.
If there is no voltage displayed, then the problem is caused by a broken wire between the EGR and the ignition bus. If 12-volts displays on one side only, the EGR has an internal open. Replace the EGR.
Pull the connector off the EGR and with the key on and the engine off, probe both outer terminals for power. Make a note of which one has 12-volts and then replace the connector.
The ground terminal is the one without the power, place a paper clip in the end of that terminal. Then, attach the jumper to the paper clip. Ground the jumper wire. You will hear a “click” as the EGR energizes. Disconnect the ground wire and start the engine. Ground the wire again, and this time the engine will begin to run roughly as the EGR is energized and smooth out as the ground is removed.
If the EGR clicked and caused the engine to run rough, the EGR is good, the problem is electrical. If not, shut off the engine and replace the EGR.
Probe the center terminal on the EGR connector. Turn the key on. There is 5.0-volts displayed if the Computer is working properly. 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 back-probe the terminal.
Turn the key on. If 5-volts is present the computer is good, and the problem is in the harness to the EGR. If no voltage is present the computer is bad.
How to Fix
Repairs for this code, of course, depend on the cause and type of damage. Common repairs include:
- Replacement of the EGR
- Replacement of the damaged or corroded connector
- Repair or replacement of the open or shorted solenoid valve harness in the EGR volume control
- Repair or replacement of poor electrical connection in the EGR volume control
- Repair or replacement of EGR temperature sensor and circuit
If your vehicle is still below 100,000 miles, it is highly recommended you read the warranty. Most vehicles have either an 80 or 100,000-mile warranty on emission controls.
Also, check online for any relevant TSBs (technical service bulletins) related to these codes and their repair procedures.
When repairing the EGR circuit without replacing the computer, check the wiring diagram and find the coolant temperature voltage reference terminal. Probe this terminal with key On. If there is a 5V reference voltage, turn the key Off and mark the two reference terminals used in these tests. Pull the connector for the computer, and then solder a jumper wire between the terminals. Install the connector, and the EGR will operate normally without replacing the computer.