Accelerator Pedal (AP) Position Sensor. Faulty Signal. Permanent Fault

Diagnostic trouble code (DTC) information

Condition




The accelerator pedal position sensor has two different internal sensors, where one generates an analogue signal and the other a pulse-width modulated (PWM) signal. The sensor for the pulse-width modulated signal (PWM) is connected to both Engine control module (ECM) and Electronic throttle module (ETM). The sensor for the analogue signal is only connected to Engine control module (ECM). Then both control modules send out the information on the CAN-net, so that other control modules have possibility to use the information.
Electronic throttle module (ETM) compares the analogue signal that comes directly from the accelerator pedal position sensor with the pulse-width modulated signal coming from the Electronic throttle module (ETM) via the CAN-net. If these two signals differ by more than 10 % for longer time than 0.5 seconds when the engine speed is higher than 600 rpm, which then stores diagnostic trouble code ECM-959F, Faulty signal. At times when the analogue signal is in the process of changing, e.g., during acceleration, a greater deviation between both signals is allowed.
For upgraded software, released during year 2006 or later, the above detection time is increased from 0.5 to 0.9 seconds.

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 Design

Substitute value

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, then slow opening of the throttle will occur and the throttle will close at braking.

Possible source
- loose connections or contact resistance in the terminals on the digital pulse width modulated signal cable
- interference on the CAN signal wiring
- fault in the pulse width modulated signal cable between the engine control module (ECM) and the throttle unit
- defective throttle unit.
- This diagnostic trouble code is generated in combination with other trouble codes. Information on the possible root cause is described.
For turbo engines and 6-cylinder aspirated engines:

Fault symptom[s]
- Poor response from accelerator
- Cruise control does not operate