Diagnostic trouble code (DTC) information

Condition 

Fig 1: Identifying Engine Control Module

Courtesy of VOLVO CARS OF NORTH AMERICA.

Diagnostic trouble code (DTC) ECM-990A is stored if the engine control module (ECM) registers that the nominal idle speed (engine coolant temperature (ECT) above 60°C) deviates, either in being 200 rpm over or 100 rpm below the nominal idle speed.

Substitute Value 

None.

Possible Source 

Faulty signal: 

• Search the air and fuel supplies in the fuel system for the fault cause (air leakage, blockages etc).
• Incorrectly adapted electronic throttle unit.

Fault symptom[s] 

• Malfunction indicator lamp (MIL) lit
• High idling speed
• Low idling speed