Technical Description of OBD-II Trouble Code
The control circuit for Exhaust Gas Recirculation (EGR) “B” is experiencing low voltage.
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles with an Exhaust Gas Recirculation system. This includes vehicles from various brands such as Land Rover, GMC, Chevrolet, Dodge, Chrysler, Ford, Toyota, Honda, etc. While the code is generic, the specific repair steps may vary depending on the make and model of the vehicle.
This engine trouble code indicates a failure in the electrical aspect of the EGR (exhaust gas recirculation) system. The EGR is an important component of the vehicle’s emission system, designed to prevent the formation of harmful nitrogen oxides (Nox) in the cylinders.
The EGR is controlled by the engine management computer, which opens or closes the EGR based on factors such as load, speed, and temperature to maintain the proper cylinder head temperature. The computer activates the EGR using two wires connected to an electrical solenoid. The EGR solenoid also contains a potentiometer that signals the position of the EGR’s pintle, which is the operating mechanism responsible for opening and closing the passage.
This operation is similar to dimming lights in a home. As the switch is turned, the lights get brighter as the voltage increases. In this case, the engine computer fails to detect any voltage change when attempting to open or close the EGR, indicating that it is stuck in one position. Codes P045C and P045D refer to the EGR control circuit “B” and indicate a lack of low or high voltage change to indicate EGR opening or closing. Consult a vehicle-specific repair manual to determine which circuit corresponds to the “B” EGR circuit in your particular case.
Unleaded fuel can produce Nox under extreme temperatures in the engine’s cylinders. The EGR routes a regulated amount of exhaust gas back into the intake manifold to dilute the incoming fuel mixture and reduce the cylinder head temperature below the threshold at which Nox forms.
EGR operation is essential for reasons beyond preventing Nox emissions. It allows for more advanced timing, resulting in more power without detonation, and a leaner fuel mixture for improved fuel economy.
Symptoms
The symptoms experienced will depend on the position of the pintle in the EGR at the time of failure.
Potential Causes
Possible causes for this DTC include:
Repair Procedures
If your vehicle has less than 100,000 miles, it is recommended to review your warranty. Most vehicles have an 80 or 100,000 mile warranty on emission controls. Additionally, check online for any relevant TSBs (technical service bulletins) related to these codes and their repair.
The following tools will be needed to perform these diagnostic procedures:
Open the hood and start the engine. If the engine has a rough idle, disconnect the plug on the EGR. If the engine smooths out, it indicates that the pintle is stuck in the EGR. Turn off the engine and replace the EGR.
Inspect the wire connector on the “B” EGR. There are 5 wires, with the two outer wires supplying battery voltage and ground. The center three wires are the potentiometer used to signal the computer about the amount of EGR flow. The center terminal is the 5-volt reference terminal.
Thoroughly inspect the connector for pushed out pins, corrosion, or bent pins. Examine the wiring harness closely for any missing insulation or potential shorts. Look for broken wires that could cause an open circuit.
A tip for repairing the EGR circuit without replacing the computer: Refer to the wiring diagram and locate the coolant temperature voltage reference terminal. Probe this terminal with the key on. If the 5-volt reference voltage is present, turn the key off and mark the two reference terminals used in these tests. Disconnect the computer’s connector, solder a jumper wire between these two terminals, and then reinstall the connector. The EGR will operate normally without the need to replace the computer.
