Diagnostic Trouble Code (DTC) Information

Condition 

The control module receives information from the heated oxygen sensor (HO2S) about the fuel / air mixture when idling at both the lower and upper part-load range. If the fuel / air mixture deviates from λ=1, the short-term fuel trim will compensate for this by adjusting the injection time so that λ=1 is achieved. When the short-term fuel trim makes an adjustment, the integrator median must be adjusted by the long-term trim. Diagnostic trouble code (DTC) ECM-271A will be stored when the long-term trim must be adjusted to almost maximum in the lower part load area.

Substitute Value 

none

Possible Source 

Upper limit: 

• intake air leakage
• exhaust system air leakage
• low fuel pressure
• defective heated oxygen sensor (HO2S)

Lower limit: 

• intake air leakage
• high fuel pressure
• leaking injectors
• defective mass air flow (MAF) sensor
• contaminated engine oil
• oil level too high
• defective heated oxygen sensor (HO2S)

Fault symptom[s] 

• none