Diagnostic trouble code (DTC) information ECM-120D

Condition 

Fig 1: Identifying Mass Air Flow (MAF) Sensor

Courtesy of VOLVO CARS OF NORTH AMERICA.

The engine control module (ECM) checks the signal from the intake air temperature (IAT) sensor under two different driving conditions. First at a high air flow with vehicle speed, then at idle speed and a stationary vehicle.

The diagnostic trouble code (DTC) is stored if the engine control module (ECM) registers that the temperature difference at these two measurement points is implausibly similar.

Substitute Value 

• The value for the intake air temperature (IAT) is set at 30 °C.

Possible Source 

• Contact resistance in the connectors
• Damaged intake air temperature (IAT) sensor.

Fault symptom[s] 

• Malfunction indicator lamp (MIL) lit.