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.