VOLVO
ECM-P040936 - Exhaust Gas Recirculation Sensor A Circuit. FM (Frequency Modulated) / PWM (Pulse Width Modulated) Failures. Signal frequency too low
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
5 modelsS80 (2007–), V70 (2008–), XC60 (2009–), XC70 (2008–), XC90 (2003–)
Show models by year and engine (6)
- Volvo S80 (2007–)2007–2009Engine D5244T4, D5244T5 only
- Volvo V70 (2008–)2008–2009Engine D5244T4, D5244T5 only
- Volvo XC60 (2009–)2009All engines except: B6304T2
- Volvo XC70 (2008–)2008All engines except: B6324S
- Volvo XC70 (2008–)2009Engine D5244T4, D5244T5 only
- Volvo XC90 (2003–)2013–2014Engine D5244T18, D5244T5 only
What does this fault code mean?
The code is named for a signal frequency that is too low. The ECM monitors the PWM signal from the EGR valve position sensor and sets the code when that signal is incorrect.
Possible causes
- Fault codes ECM-P040937 and ECM-P040938 may share the same cause and should be read together
- EGR valve is stuck in the open or closed position
- Sticking EGR valve
- Damaged position sensor or damaged EGR valve
- Contact resistance or oxidation in the connectors
- Break in the signal cable
What you can do
- 1If you have a diagnostic tool, read the fault status with the engine running and see whether it is active or only stored
- 2Check that the EGR valve moves without sticking while the engine runs
- 3Check that the connectors to the position sensor are firmly seated and not oxidised
- 4Use a multimeter to check that the signal cable has no open circuit
- 5Clean the EGR valve of dirt and soot if needed
- 6If the fault remains, have a workshop check the position sensor and the EGR valve
Symptoms you may notice1
- The Check engine (malfunction indicator) light comes on or behaves abnormally
What the fault can affect1
- EGR control is lost
General guidance for car owners. Diagnosis on the car can point to a different cause.