Diagnostic Trouble Code (DTC) Information ECM-903F

Condition

Fig 1: Identifying PWM Signals From Accelerator Pedal Position Sensor To ETM

Courtesy of VOLVO CARS OF NORTH AMERICA.

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 regulates to the desired throttle angle and sends back information on current throttle angle. 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 by more than 5% for 0.42 seconds, it stores diagnostic trouble code ECM-903F, no signal. When the desired throttle angle is undergoing major change, such as during throttle application, a greater deviation between the desired and actual throttle angle is allowed.

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 the engine control module (ECM) detects that the electronic throttle module (ETM) transmits something other than AAAA, it stores diagnostic trouble code ECM-903F, high signal.

The above tests are only active when engine speed exceeds 700 RPM.

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 2 % 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 high

The detection time is changed from 0.4 seconds to 2.6 seconds.

See Identifying upgraded software ECM/ETM

For more information about the electronic throttle system and related components such as the electronic throttle module, accelerator pedal position sensor, brake light switch, clutch pedal position sensor, and brake pedal position sensor:Design

See Function

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 driving cycles when the fault is active, fuel shut-off that follows the accelerator pedal position will be activated.

See Identifying upgraded software ECM/ETM

Possible Source

Signal missing:

low power supply to the electronic throttle module (ETM) (loose terminals or contact resistance in the terminals, low system voltage)
Damaged CAN cables.
Disruptions on CAN signal cables.
defective 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).
Damaged CAN cables.
Disruptions on CAN signal cables.
Loose connections or contact resistance in connections to CAN-net.

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.

HINT: Information about combined diagnostic trouble codes (DTCs)

Fault symptom[s]

the accelerator pedal (AP) is ignored when braking
the cruise control is not functioning at all
uneven idle
jerks during engine braking.