H1 - Check For Diluted Engine Oil

DIAGNOSTIC TROUBLE CODES (DTC)
136r Left/front Heated Oxygen Sensor (HO2S) lean.
137r Left/front HO2S rich.
139c Left/front HO2S not switching.
144c Right/rear HO2S not switching.
171c Adaptive fuel limit reached on right/rear HO2S.
172r Right/rear HO2S lean.
173r Right/rear HO2S rich.
175c Adaptive fuel limit reached on left/front HO2S.
176c Left/front HO2S lean.
177c Left/front HO2S rich.

NOTE: A DTC followed by an "r" indicates an on demand code, while a "c" indicates a continuous memory code.

Possible Causes:

- Fuel injectors.

- HO2S.

- Secondary Air Injection (AIR) system.

- Positive Crankcase Ventilation (PCV)/Hose.

- Vacuum.

- Evaporative Cannister Purge.

- Manifold Absolute Pressure (MAP) sensor.

- Electronic Ignition Coil Failure.

- Key "OFF".

- Remove the PCV valve from the valve cover. Inspect both rocker cover hole and PCV for damage, sludge build up, blockage and movement of valve plunger. Service as necessary.

- Run Key On Engine Off (KOEO) and Key On Engine Running (KOER) Self-Tests. Quick Test Appendix (Detailed Testing Instructions)

- Address any continuous ignition DTCs before servicing KOER DTCs.

NOTE: For a No Start, go directly to H2. H2 - Check Fuel Pressure

- Are any of the above DTCs present in KOER Self-Test?

Yes -- Reinstall PCV valve. Go to H2. H2 - Check Fuel Pressure

No -- For Continuous Memory DTCs 139, 144, 171, 176, 177 Go to H2. H2 - Check Fuel Pressure

All Others: Change engine oil and filter. Reinstall PCV valve. Drive vehicle 5 miles/55mph. Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)