Error Code P045B is defined as Exhaust Gas Recirculation B Control Circuit Range.

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 job of the EGR (Exhaust Gas Recirculation) system is to redirect exhaust gas back into the cylinders. Since exhaust gas is inert, it displaces O2 (oxygen) and fuel, thereby lowering the cylinder temperature, which in the process, lowers nitrogen oxide emissions. For this, it must be metered carefully into the cylinders (through EGR valve) so as not to adversely affect the performance of the engine, as too much EGR will keep the engine from idling.

Error code P045B happens when the EGR valve is likely an electrically controlled valve, instead of a vacuum controlled EGR valve. Also, the valve usually comes with a built-in feedback system that tells the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) about the position of the valve; open, closed, or somewhere in between. The PCM need to know the position to determine whether or not the valve is running as needed.

If the PCM determines that the valve should be running, but the feedback circuit shows it’s not open, then the Error Code P045B will be set. Or if the valve should be closed, but the feedback signal shows it is open.

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. In many cases, there are usually no drivability or performance symptoms for the vehicle associated with this code.

The EGR systems, however, are inherently problematic due to the buildup of carbon in the intake manifold, etc. Normal buildup can cause lodge in an EGR valve, holding it open when it should be closed. If this is the case, then the engine may idle rough, or not at all.

If the valve has failed and not working, then the symptoms would be higher combustion temperature, which results in higher NOx emission. This symptom, however, can be hard to notice.

Possible Causes

The usual cause of this code is carbon buildup or defective EGR valve. Other possible causes include:

  • Open or short in the ground circuit
  • Open or short in the 5 Volt reference circuit
  • Open or short in the PCM controlled voltage circuit
  • Bad PCM (rare)

How to Check

Should you get this code, it is highly recommended that you refer to the vehicle’s specific repair guide for the specific year, make, and model of the engine. Also, refer to a vehicle specific repair manual to determine which is the “B” EGR circuit in your particular case.

Diagnosing this code requires a scan tool to command the EGR valve “B” to open while watching the actual EGR position (it will be labeled with “desired EGR” or something similar). The actual EGR position must be close to the “desired” EGR position. If it is, then the problem must be intermittent, which may have been caused by a lodged piece of carbon that is dislodged, or it must be a case of a bad EGR valve winding intermittently opens or shorts as the temperature of the valve changes.

If the “desired” position is NOT close to the “actual” position, then unplug the EGR sensor and check if there’s a 5V reference voltage in the connector. If it doesn’t show reference voltage, then repair the open or short in the 5V reference circuit.

However, if there’s a 5V reference voltage, then activate the EGR with the scanner, and then monitor the EGR ground circuit using a DVOM (digital volt/ohm meter). It should show good ground. If it doesn’t have a good ground, then repair the ground circuit.

If there is good ground, then check the control circuit; it must indicate the voltage that varies according to the percentage that the EGR is open. The voltage should increase accordingly as it opens. If it does, then the EGR valve must be replaced.

If the voltage doesn’t increase incrementally, then repair open or short in EGR control circuit.

How to Fix

Common repairs for this code include:

  • Repair open or short in the 5V reference circuit
  • Repair ground circuit
  • Replacement of the EGR valve
  • Repair open or short in EGR control circuit

This entry only shows general information about the code. Make sure you also check the Technical Service Bulletins (TSB) that may apply to your vehicle.