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-91C7 is stored if the engine control module (ECM), when attempting to adapt the throttle unit, registers that the movements of the throttle is impeded or that the opening spring in the throttle unit is not functioning correctly.

Substitute Value 

Depending on the fault, the engine control module (ECM) can cut off the supply to the damper motor in the throttle unit. The throttle will then attempt to 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.