Diagnostic Trouble Code (DTC) Information ECM-91A7

Condition 

Fig 1: Identifying Throttle Unit & Potentiometer

Courtesy of VOLVO CARS OF NORTH AMERICA.

The diagnostic trouble code (DTC) is stored if the engine control module (ECM) registers that the throttle angle requested by the engine control module (ECM) (desired value) does not correspond to the actual throttle angle (actual value) in the electronic throttle unit. The diagnostic trouble code (DTC) is diagnosed when the engine is idling.

Substitute Value 

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

Possible Source 

• 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 electronic 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
• Damaged throttle unit.

Fault symptom[s] 

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