VOLVO
ECM-958F - Accelerator pedal (AP) position sensor. Faulty signal. Intermittent fault
System
Engine Control Module (ECM)
Volvo models this fault code applies to
This fault code has different meanings depending on model, model year or engine. Select the meaning that applies to your car.
Applies to the following models:
5 modelsC70 Cabriolet (1998–2005), C70 Coupé (1998–2002), S70 (1997–2000), V70 (1997–2000), V70 XC (1998–2000)
Show models by year and engine (10)
- Volvo C70 Cabriolet (1998–2005)1999, 2001–2002
- Volvo C70 Cabriolet (1998–2005)2000All engines except: B5244S
- Volvo C70 Coupé (1998–2002)1999All engines except: B5254S DENSO
- Volvo C70 Coupé (1998–2002)2000All engines except: B5244S
- Volvo C70 Coupé (1998–2002)2001–2002
- Volvo S70 (1997–2000)1999Engine B5204T3, B5204T4, B5234T3, B5234T7, B5254T only
- Volvo S70 (1997–2000)2000Engine B5204T3, B5204T4, B5234T3, B5234T7, B5244T only
- Volvo V70 (1997–2000)1999Engine B5204T3, B5204T4, B5234T3, B5234T7, B5234T8, B5254T only
- Volvo V70 (1997–2000)2000All engines except: B5244S, B5244S2, B5244SG, B5244SG2, D5252T MSA 15.8
- Volvo V70 XC (1998–2000)1999–2000
What does this fault code mean?
The fault is intermittent, meaning it has occurred at some point but may not be present now. The ECM checks the analogue pedal signal against the PWM signal and stores the code if the difference grows too large for a longer time. A larger deviation is allowed while the analogue signal is changing, for example during acceleration.
Possible causes
- Connector problem on the analogue signal wire, with loose contact or increased resistance
- Open circuit in the supply to the pedal sensor
- Open circuit in the ground wire
- The PWM wire between the engine control module and the throttle module is faulty
- Damaged system relay
- Damaged accelerator pedal position sensor
What you can do
- 1First fix the codes ECM-9520 or ECM-9530 if they are stored, since they should be troubleshot first
- 2Read the fault code counter to see whether the fault is intermittent or permanent. In live data, compare analogue and PWM pedal values
- 3In live data, press the pedal down slowly and release it through its full travel. If either signal deviates at a certain pedal position, this points to a defective pedal sensor
- 4Check the wiring and connectors between the pedal sensor and the engine control module for contact resistance and corrosion, and for potential differences in the ground connections
- 5Check the battery condition. If upgraded software exists for the car (released 2006 or later), it may solve the fault because it tolerates brief disturbances better. A workshop can load it
- 6After repair: clear the code and let the ignition stay off for a while before test driving, so the throttle module resets
Symptoms you may notice1
- Poor accelerator pedal response
What the fault can affect3
- The throttle opens more slowly than normal, since it is then controlled by one signal only
- The throttle closes when braking
- The accelerator pedal position is ignored while the brake pedal is pressed
General guidance for car owners. Diagnosis on the car can point to a different cause.