Technical Description of OBD-II Trouble Code
High Control Circuit for Exhaust Gas Recirculation “B”
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles with an Exhaust Gas Recirculation system. Vehicle brands such as Land Rover, GMC, Chevrolet, Dodge, Chrysler, Ford, Toyota, Honda, etc., may be included. Although it is a generic code, the specific repair steps may vary depending on the make and model.
These engine trouble codes indicate a failure in the electrical aspect of the EGR (exhaust gas recirculation) system. The EGR is an integral part of the vehicle’s emission system, and its function is to prevent the formation of harmful Nox (oxides of nitrogen) in the cylinders.
The engine management computer operates the EGR. It opens or closes the EGR based on load, speed, and temperature to maintain the proper cylinder head temperature. The computer activates the EGR using two wires connected to the electrical solenoid on the EGR. The EGR solenoid also contains a potentiometer that signals the position of the EGR’s pintle, which is the operating mechanism that opens and closes 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. However, 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 P045D EGR control circuit “B” means there is no high voltage change to indicate the EGR is opening or closing. P045C is essentially the same, but it means the circuit is low instead of high. Consult a vehicle-specific repair manual to determine which is the “B” EGR circuit in your particular case.
Unleaded fuel tends to produce Nox when exposed to 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 sufficiently and reduce the cylinder head temperature below the point at which Nox forms.
EGR operation is essential for more than just preventing Nox emissions. It allows for more advanced timing, resulting in more power without detonation, and a leaner fuel mixture for better fuel economy.
Symptoms
The symptoms will vary depending on the position of the pintle in the EGR at the time of failure.
Potential Causes
The potential causes for this DTC may include:
Repair Procedures
If your vehicle has less than 100,000 miles, it is advisable 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.
To perform these diagnostic procedures, the following tools will be needed:
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 outside 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. Also, closely examine the wiring harness for any missing insulation or possible 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 replacing the computer.
