VOLVO
ECM-P040938 - Exhaust Gas Recirculation Sensor A Circuit. FM (Frequency Modulated) / PWM (Pulse Width Modulated) Failures. Signal frequency incorrect
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 fault concerns the frequency of the PWM signal from the EGR valve position sensor being incorrect. The ECM monitors the signal and sets the code when it is wrong.
Possible causes
- EGR valve has jammed in the open position
- EGR valve has jammed in the closed position
- Sticking EGR valve
- Damaged position sensor
- Damaged EGR valve
- Contact resistance or oxidation in the connectors
What you can do
- 1If you have a diagnostic tool, read the fault status with the engine running and see whether the fault is active
- 2Check that the EGR valve does not stick in any position when it is driven
- 3Check the connectors to the position sensor for oxidation and contact resistance
- 4Check the signal cable for breaks, particularly near the connectors
- 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.