Diagnostic Trouble Code (DTC) Information

Diagnostic trouble code (DTC) information ECM-903F

Condition




The engine control module (ECM) sends a request for the desired throttle angle to the electronic throttle module (ETM) via the CAN network. The electronic throttle module (ETM) fulfills the desired throttle angle and sends back information on current throttle position. If the engine control module (ECM) detects that the current throttle angle, which comes from the electronic throttle module (ETM), deviates from the desired angle, it stores diagnostic trouble code ECM-903F, low signal or no signal.
Diagnostic trouble code ECM-903F, Signal missing, is stored when the desired throttle angle is stable and the deviation is greater than 5% for 0.5 seconds.
Diagnostic trouble code ECM-903F, Too low signal, is stored when desired throttle angle is under heavy change, e.g., during acceleration, and the deviation is greater than 20 % for 0.5 seconds.
The above test is only active when engine speed exceeds 600 rpm.
The diagnostic trouble code also includes a check that software in the electronic throttle module (ETM) has time to carry out the instructions and calculations it is expected to do in each work cycle. After each work cycle, the electronic throttle module (ETM) sends a code to the engine control module (ECM) via the CAN network. After a correctly completed work cycle, the code should be AAAA. If Engine control module (ECM) detects that Electronic throttle module (ETM) sends anything else than AAAA for longer time than 0.5 seconds, then diagnostic trouble code ECM-903F, Too high signal, is stored.
For upgraded software, released during year 2006 or later, certain adjustments have been made.

Signal missing
When it comes to the comparison between desired throttle angle and current throttle angle, the Engine control module (ECM) must have received the current throttle angle from the Electronic throttle module (ETM) on the CAN-net, before the test is activated. The deviation between desired throttle angle and actual throttle angle is changed from the fixed value of 5 %, across the whole range, to a variable limit. The variable limit is within 5 % deviation at 10 % desired throttle angle, it is then increased up to 10 % deviation at 50 % desired throttle angle. In order for it to be considered a deviation, is requires that the current throttle angle is greater than the desired throttle angle, which is a difference from before. Then the diagnostic trouble code was also generated if the desired throttle angle was greater than the current throttle angle.

Signal too low
When it comes to the comparison between desired throttle angle and current throttle angle, the Engine control module (ECM) must have received the current throttle angle from the Electronic throttle module (ETM) on the CAN-net, before the test is activated. In order for it to be considered a deviation, is requires that the current throttle angle is 20% greater than the desired throttle angle, which is a difference from before. Then the diagnostic trouble code was also generated if the desired throttle angle was greater than the current throttle angle. Another condition has been added to this. Engine control module (ECM) calculates the air mass in to the engine using, among other, information about the throttle position, engine rpm, EVAP-flow, air temperature, atmospheric pressure and pressure in the intake manifold. Then the measured air mass from the mass air flow sensor is compared with the calculated air mass. If Engine control module (ECM) registers that the measured air mass is sufficiently greater than the calculated air mass, then diagnostic trouble code ECM-903F, Too low signal, is stored.

Signal too high
The detection time is changed from 0.5 seconds to 2.5 seconds.
Identifying upgraded software ECM/ETM Testing and Inspection

Substitute value

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.

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.
For upgraded software, released in 2006 or later, adjustments have been made to substitute values. In the driving cycles where the fault is active, then fuel shut-off which follows the accelerator pedal position will be active and cruise control will be shut off.
Identifying upgraded software ECM/ETM Testing and Inspection

Possible source

Signal too low/Signal missing
- Low voltage feed to electronic throttle module (loose connections or contact resistance in connections, low system voltage).
- Damaged CAN cables.
- Disruptions on CAN signal cables.
- Damaged electronic throttle module (ETM).

Signal too high Software not upgraded.
- Incorrect software in Engine control module (ECM) or Electronic throttle module (ETM).
- Low voltage feed to electronic throttle module (loose connections or contact resistance in connections, low system voltage).
- Loose connections or contact resistance in connections to CAN-net.
- Damaged CAN cables.
- Disruptions on CAN signal cables.

Signal too high. Upgraded software.
- Incorrect software in Engine control module (ECM) or Electronic throttle module (ETM).

Hint: This diagnostic trouble code is generated in combination with other trouble codes. Information on the possible root cause is described.
Information about combined diagnostic trouble codes (DTCs) Information About Combined Diagnostic Trouble Codes (DTCs)

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.