Diagnostic Trouble Code (DTC) Information

Diagnostic trouble code (DTC) information EFI-231, EFI-232

EFI-231 Long-term fuel trim, part load EFI-232 Long-term fuel trim, idling speed

Condition




The engine control module (ECM) receives information from the heated oxygen sensor (HO2S) about the fuel/air mixture in the idling and partial load ranges. If the fuel/air mixture deviates from lambda=1 the short-term fuel trim will compensate for this by adjusting injection time so that lambda=1 is achieved. When the short-term fuel trim makes an adjustment, the integrator median must be adjusted by the long-term trim. If adaptation needs to adjust to close to its maximum diagnostic trouble code (DTC) EFI-232 (idling range -0.48 ms - 0.40 ms) or diagnostic trouble code (DTC) EFI-231 (part load range factor 0.773 - 1.227) and the status message Upper limit (lean fuel/air mixture) or Lower limit (rich fuel/air mixture) will be stored.

Substitute value
- none.

Possible source

UPPER LIMIT
- defective mass air flow (MAF) sensor
- low fuel pressure
- air leakage
- faulty pulsation damper
- faulty sensor signals.

Lower limit:
- defective mass air flow (MAF) sensor
- high fuel pressure
- leaking injectors
- leaking evaporative emission (EVAP) system
- contaminated engine oil
- oil level too high
- faulty sensor signals.

Fault symptom[s]
- can result in high fuel consumption
- may result in poor performance