VOLVO
ECM-8400 - 5 volt power supply. Signal too low. Intermittent fault
System
Engine Control Module (ECM)
Volvo models this fault code applies to
This fault code has different meanings depending on model, model year or engine. Select the meaning that applies to your car.
Applies to the following models:
7 modelsC70 Cabriolet (1998–2005), C70 Coupé (1998–2002), S60 (2001–2009), S70 (1997–2000), S80 (1999–2006), V70 (1997–2000), V70 (2000–2008)
Show models by year and engine (14)
- Volvo C70 Cabriolet (1998–2005)2000Engine B5244S only
- Volvo C70 Coupé (1998–2002)1999Engine B5254S DENSO only
- Volvo C70 Coupé (1998–2002)2000Engine B5244S only
- Volvo S60 (2001–2009)2001Engine B5244S, B5244S2 only
- Volvo S60 (2001–2009)2002Engine B5244S, B5244S2, B5244SG, B5244SG2 only
- Volvo S70 (1997–2000)1999Engine B5254S DENSO only
- Volvo S70 (1997–2000)2000Engine B5244S, B5244S2, B5244SG, B5244SG2 only
- Volvo S80 (1999–2006)1999–2000Engine B5244S, B5244S2 only
- Volvo S80 (1999–2006)2001Engine B5244S, B5244S2, B5244SG only
- Volvo S80 (1999–2006)2002Engine B5244S, B5244S2, B5244SG, B5244SG2 only
- Volvo V70 (1997–2000)1999Engine B5254S DENSO only
- Volvo V70 (1997–2000)2000Engine B5244S, B5244S2, B5244SG, B5244SG2 only
- Volvo V70 (2000–2008)2001Engine B5244S, B5244S2, B5244SG only
- Volvo V70 (2000–2008)2002Engine B5244S, B5244S2, B5244SG, B5244SG2 only
What does this fault code mean?
The engine control module (ECM) monitors the supply voltage to several of the engine sensors. The code is set when the supply is too low, for example if a wire is shorted to ground. The fault is intermittent: it has occurred on an earlier occasion but is not present right now.
Possible causes
- The signal wire is shorted to ground, so the signal becomes too low
- Intermittent short to ground in the wiring harness that only happens now and then
What you can do
- 1Read the code, clear it and road test the car to see whether it comes back
- 2Go through the sensor wiring and look for chafing or crushed areas where the cable can touch ground
- 3Check that the connectors are fully engaged and free from oxidation
- 4Use a multimeter to check that the signal wire has no contact with ground (the body), and move the harness while measuring so an intermittent fault can show up
- 5If you have diagnostic equipment, watch the sensor supply voltage in live data during a road test and see whether it drops when you move the cable
- 6If the wiring shows no fault, have a workshop continue the fault finding on the control module and the sensors
Symptoms you may notice2
- Poor performance
- Uneven idle
General guidance for car owners. Diagnosis on the car can point to a different cause.