ECM-902A - Communication with throttle unit. 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) monitors the signals from the electronic throttle module (ETM) over the CAN network. The code is set when any of these signals drops out for a while during operation, while the engine is running at a sufficiently high speed. The cause may be in the supply to the throttle module, in the CAN wiring or in a control module on the network. The code can also be set together with other codes.
Possible causes
- Lack of voltage supply to the throttle module
- Loose connections or contact resistance at the CAN connections
- Open circuit in one or both CAN signal wires
- Short to ground, to voltage or between the CAN wires
- Interference on the CAN wiring
- A defective node or a damaged control module in the CAN network
What you can do
- 1Check that the throttle module receives voltage when the ignition is switched on; use a multimeter to confirm the supply is present and not too high
- 2Check that the CAN wire connectors are fully engaged and free from oxidation, and confirm with a multimeter that the wires have no break or short to ground or voltage
- 3CAN codes in all control modules should be traced first, since the reconfiguration does not show the root cause
- 4If you have diagnostic equipment, read the throttle signals in live data during a road test and see whether any of them drops out
- 5If the wiring is intact, the system relay may have engaged late at start; have a workshop check the system relay and the battery
- 6If the fault returns after these checks, have a workshop check the control modules and the nodes in the CAN network
Symptoms you may notice5
- The accelerator pedal is ignored when braking
- Cruise control cannot be engaged
- Uneven idle
- Jerking during engine braking
- On the C70 and on S70 and V70 up to the year 2000, the electronic throttle warning lamp lights
What the fault can affect3
- The throttle follows the accelerator pedal position directly, and fuel cut-off follows the pedal position
- Engine speed is controlled by fuel cut-off, so idle may feel uneven
- Cruise control is 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.