Diagnostic trouble code (DTC) information

Condition 

Fig 1: Identifying Throttle Unit And Potentiometer

Courtesy of VOLVO CARS OF NORTH AMERICA.

Diagnostic trouble code (DTC) ECM-91A7 is stored if the engine control module (ECM) registers, when the engine is running, that the required throttle angle (desired value) does not correspond with the actual throttle angle (actual value) in the throttle unit

Substitute Value 

The engine control module (ECM) shuts down the supply to the throttle unit damper motor. The throttle will set itself to the return position

Possible Source 

Faulty signal: 

• The throttle is sticking or is blocked (oil film, dust etc.)
• Contact resistance or oxidation in the terminals between the engine control module (ECM) and the throttle unit
• Open-circuit, short-circuit to ground or short-circuit to supply voltage in the wiring for the damper motor in the throttle unit
• Short-circuit to each other in the wiring for the damper motor in the throttle unit
• Defective throttle unit.

Fault symptom[s] 

• Malfunction indicator lamp (MIL) lit
• Poor performance.