243
UnclassifiedGeneral
What This Code Means
Adaptive learn reaching its limit; Lean exhaust condition at light load; False lean condition; System operating lean; Multiple unrelated operational problems
Possible Causes
- •Crankcase leaks
- •Drastic variation in fuel quality
- •Exhaust leaks pulling outside air past the oxygen sensor
- •Faulty ECM grounds
- •Faulty HO2S sensor
- •Fuel system misadjustment or failure
- •Large vacuum leaks
- •Oxygen sensor wire mispositioned contacting the exhaust
- •Short to ground between harness and sensor or on sensor harness
- •Variations in fuel composition, engine wear, or component degradation
Suggested Actions
- 1Check and adjust fuel system according to PSI guidelines
- 2Check for short to ground between harness and sensor and on sensor harness
- 3Ensure ECM grounds have a good engine or battery ground connection
- 4If any other DTCs are present, diagnose those first
- 5If fuel system is operating to specification, replace the HO2S sensor with a known good part and retest
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