VOLVO
ECM-91AC - Throttle unit. Current too high
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:
4 modelsC30 (2007–2013), C70 (2006–2013), S40 (2004–2013), V50 (2004–2013)
Show models by year and engine (8)
- Volvo C30 (2007–2013)2007–2011Engine B5244S4 only
- Volvo C70 (2006–2013)2006All engines except: B5254T3
- Volvo C70 (2006–2013)2007–2010Engine B5244S4, B5244S5 only
- Volvo C70 (2006–2013)2011Engine B5244S4 only
- Volvo S40 (2004–2013)2004Engine B5244S4, B5244S5 only
- Volvo S40 (2004–2013)2005–2010Engine B5244S4, B5244S5, B5244S7 only
- Volvo V50 (2004–2013)2004Engine B5244S4, B5244S5 only
- Volvo V50 (2004–2013)2005–2010Engine B5244S4, B5244S5, B5244S7 only
What does this fault code mean?
The ECM verifies that the throttle reaches the angle it has asked for. If it detects a fault linked to the throttle unit's motor or its control, the code is set. The fault can be a sticking throttle, wiring that is short-circuited or open, or a damaged throttle unit or engine control module.
Possible causes
- The throttle is stuck or sticking, for example from dirt, oil film or ice
- Damaged throttle unit
- Faulty signal from the throttle unit to the engine control module
- Wiring to the throttle unit short-circuited to voltage or ground
- Open circuit in the wiring to the throttle unit
- Damaged engine control module
What you can do
- 1Check that the throttle is not sticking or blocked, and clean it if necessary
- 2Check the connectors at the throttle unit and the engine control module for contact resistance and oxidation
- 3Use a multimeter to check that the two damper motor wires are not short-circuited to each other and have no contact with ground or voltage
- 4If the fault remains, have a workshop assess the throttle unit and the engine control module, and carry out the adaptation after any replacement
Symptoms you may notice2
- The engine produces less power than normal
- The idle is uneven
What the fault can affect2
- The cruise control is switched off while the fault is active
- The throttle returns to its spring-returned position, because the supply to it is switched off
General guidance for car owners. Diagnosis on the car can point to a different cause.