Diagnostic trouble code (DTC) information ECM-91AC

Condition

Fig 1: Identifying Electronic Throttle Module (ETM)

Courtesy of VOLVO CARS OF NORTH AMERICA.

The engine control module (ECM) checks that the throttle follows the requested throttle angle from the engine control module (ECM). The diagnostic trouble code (DTC) is stored if a fault related to the engine or control of the engine in the throttle unit is detected.

The diagnostic trouble code (DTC) can be diagnosed when the car has been test-driven in various driving conditions.

Substitute Value

The cruise control is disengaged when the fault is active
The supply to the throttle unit is switched off, causing the throttle disc to turn to the return position.

Possible Source

Throttle jammed

The throttle is sticking or is blocked (e.g. dirt, icing, etc.)
Damaged throttle unit.

Faulty signal

The throttle is sticking or is blocked (e.g. oil film, dust, icing)
Damaged throttle unit
Damaged engine control module (ECM).

Actuator current too high

Short-circuit to supply voltage or ground in the wiring for the throttle unit
Open-circuit in the wiring for the throttle unit
Damaged throttle unit
Damaged engine control module (ECM).

Fault symptom[s]

Deterioration in performance
Uneven idle
Cruise control does not function at all.