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Trouble Code Conditions

EFI-231 LONG-TERM FUEL TRIM, PART LOAD
EFI-232 LONG-TERM FUEL TRIM, IDLING





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 optimum the short term fuel trim will compensate for this by adjusting injection time so that optimum mixture is achieved. When the short-term fuel trim makes an adjustment, the integrator median must be adjusted by the long-term trim. When adaptation is almost at its maximum level diagnostic trouble code (DTC) EFI-232 (idling range - 0.48 ms to + 0.40 ms) or diagnostic trouble code (DTC) EFI-231 (part load range 0.773ms to 1.227ms) 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(s)

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

OTHER DIAGNOSTIC TROUBLE CODES AND STATUS MESSAGES





Other diagnostic trouble codes (DTCs)

- Read off other diagnostic trouble codes (DTCs).
- Is diagnostic trouble code (DTC) EFI-315 stored?

Yes:
- See Code EFI-315 Canister Purge Valve Leakage

No:
- Proceed to test step below.





Status messages

- Select one of the following options to continue.

Alternative 1:
- Proceed to Upper Limit section.

Alternative 2:
- Proceed to Lower Limit section.