Diagnostic Trouble Code (DTC) Information

Diagnostic trouble code (DTC) information ECM-901A

Condition




The control modules communicate with each other in a network via standardized serial communication - CAN (controller area network). The diagnostic trouble code is generated if the engine control module (ECM) registers a serious disruption on the CAN network (CAN communication blocked).
For upgraded software, released during year 2006 or later, this diagnostic trouble code is removed.

Substitute value
The engine control module (ECM) shuts itself off "bus-off".

Hint: The engine control module (ECM) will be off until the power supply has been cut off (15, 30 or X-feed). When the power supply is connected, the engine control module (ECM) will make a new attempt to communicate.

Fuel cut-off that follows accelerator pedal position.
Engine speed is regulated via fuel cut-off by deactivating the injectors one at a time. Engine speed is determined by gas pedal position sensor position and engine speed is maximized to about 5000 rpm.
This reconfiguration can cause the engine to idle very unevenly since the engine control module (ECM) regulates engine speed by cutting of the fuel to the cylinders individually. Do not confuse this reconfiguration (engine behavior) with an actual driveability problem that was present before reconfiguration.

Closing of throttle during braking.
The accelerator pedal position is ignored when the brake pedal is depressed.

Throttle follows accelerator pedal position.
The throttle and accelerator pedal are used as if they were mechanically connected. This reconfiguration is always followed by fuel cut-off.

Cruise control off.
Cruise control off during entire operating cycle in which fault was detected. If the fault is no longer present, the function is available the next time the car is started.

Possible source
- loose connections or contact resistance in the terminals for the CAN
- open-circuit in one or both CAN signal cables
- short-circuit to ground, voltage or each other in one or both of the CAN signal cables
- interference on the CAN signal wiring
- defective node in the Control area network (CAN).

Fault symptom[s]
- the accelerator pedal (AP) is ignored when braking
- the cruise control cannot be activated
- uneven idle
- jerks during engine braking
- ETS warning lamp lit