H51 - Check HO2S Integrity

Diagnostic Trouble Codes (DTCs) 1131 and 1151 and/or 1130 and 1150 indicate HO2S always lean, slow to switch, lack of switching or fuel at adaptive limit.

Possible Causes:
- Moisture inside the HO2S harness connector resulting in a short to ground.
- HO2S coated with contaminates.
- HO2S circuit open.
- HO2S circuit shorted to ground.

- Key Off.

- Inspect HO2S harness for chaffing, burnt wires or other damage and service.

- Inspect HO2S and connector for indications of submersions in water, oil, coolant, etc., and service.

- Run engine at 2000 rpm for two minutes.

- Key Off.

- Activate Key On Engine Running (KOER) Self-Test.

- Are there codes present?

YES -- Go to H52. H52 - Check HO2S Ability to Generate Voltage Greater Than 0.5 V

NO -- HO2S system is OK. Fuel delivery system is OK. Faults may have been repaired while doing inspection. Testing is complete at this time.