VOLVO
ECM-901A - Engine control module (ECM) communication. Faulty signal
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 (20)
- 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 S60 (2001–2009)2003–2005Engine B5244SG, B5244SG2 only
- Volvo S60 (2001–2009)2006–2008Engine B5244SG 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 S80 (1999–2006)2003–2005Engine B5244SG, B5244SG2 only
- Volvo S80 (1999–2006)2006Engine B5244SG 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
- Volvo V70 (2000–2008)2003–2005Engine B5244SG, B5244SG2 only
- Volvo V70 (2000–2008)2006–2008Engine B5244SG only
What does this fault code mean?
The engine control module (ECM) sets the code when it picks up a serious disruption on the CAN network, the network over which the control modules in the car exchange information. When communication is blocked the throttle may be reconfigured and the car's drivability suffers. The fault may lie in the wiring, the connectors or a node on the network.
Possible causes
- Loose connections or contact resistance at the CAN network connectors
- Break in one or both CAN signal wires
- Short to ground, to voltage or between the CAN wires
- Interference on the CAN signal wires
- A defective node in the CAN network
What you can do
- 1Check that the connectors in the CAN network are fully engaged and not oxidised
- 2Use a multimeter to confirm the CAN wires have no break and are not shorted to ground or voltage
- 3Look for chafed wires in the CAN network, especially where they run close to other cables
- 4Read the CAN codes in the other control modules first, since this code may be a result of them
- 5If the fault returns after these checks, have a workshop check the nodes in the CAN network that may be defective
Symptoms you may notice4
- The accelerator pedal is ignored when braking
- Cruise control cannot be engaged
- Uneven idle
- The electronic throttle system warning lamp is on
What the fault can affect3
- The engine control module shuts itself off (bus-off) and stays off until the power supply is cut
- The throttle follows the accelerator pedal position, and engine speed is controlled by fuel cut-off
- Cruise control is switched off during the driving cycle in which the fault was detected
General guidance for car owners. Diagnosis on the car can point to a different cause.