Diagnostic trouble code (DTC) information ECM-950F

Condition

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

Courtesy of VOLVO CARS OF NORTH AMERICA.

Engine control module (ECM) receives information about the accelerator pedal's position via the accelerator pedal position sensor's two internal position sensors, where one generates an analogue signal and the other a pulse-width modulated signal (PWM). If Engine control module (ECM) registers that there is a difference of more than 5 % between the two sensors' signals for longer time than 0.4 seconds, then diagnostic trouble code ECM-950F, Faulty signal, is stored. 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 model years 1999-2001, an engine speed higher than 700 rpm is required for the test to be active. For model year 2002-, the test is active when the ignition is on.

For upgraded software, released during year 2006 or later, the above detection time is increased from 0.4 to 0.7 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:

See Design
See Function

Substitute Value

Slow opening of throttle.

The throttle opens slower than during normal requested open because the system is regulated by only one of the pulse width modulated signals from the accelerator pedal position sensor. The driver may notice that the engine responds a bit slower compared to normal throttle application.

Closing of throttle during braking.

The accelerator pedal position is ignored when the brake pedal is depressed.

Possible Source

Loose connections or contact resistance in the terminals on the analog signal cable
Open-circuit in the power supply for the accelerator pedal (AP) position sensor
Open-circuit in the ground lead for the accelerator pedal (AP) position sensor
Fault in the PWM signal between the engine control module (ECM) and the electronic throttle module (ETM)
Defective system relay
Defective accelerator pedal (AP) position sensor.

This diagnostic trouble code is generated in combination with other trouble codes. Information on the possible root cause is described.

See Information about combined diagnostic trouble codes (DTCs)

Fault symptom[s]

Poor accelerator pedal (AP) response.