Trouble Code Conditions
EFI-231 LONG-TERM FUEL TRIM, PART LOADEFI-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.