Diagnostic trouble code (DTC) information ECM-250A

Condition 

Fig 1: Identifying Mass Air Flow Sensor

Courtesy of VOLVO CARS OF NORTH AMERICA.

The engine control module (ECM) receives information from the heated oxygen sensor (HO2S) about the fuel/air mixture at different loads. The diagnostic trouble code (DTC) is stored if the engine control module (ECM) registers that the fuel/air mixture deviates too much from target lambda value, leaving the long-term trim in one of its limit positions.

Substitute Value 

None.

Possible Source 

Upper limit: 

• Damaged mass air flow (MAF) sensor
• Low fuel pressure
• Air leakage.

Lower limit: 

• Damaged mass air flow (MAF) sensor
• High fuel pressure
• Leaking injectors
• Leaking evaporative emission system (EVAP)
• Contaminated engine oil
• Oil level too high.

Fault symptom[s] 

• Malfunction indicator lamp (MIL) lit
• Poor performance
• May result in high fuel consumption.