HB21 - Attempt to Generate DTC 136, 172, or 176

- Key "OFF".

- Heated Oxygen Sensor (HO2S) disconnected.

- Jumper HO2S circuit at the HO2S vehicle harness connector to battery negative post.

- Rerun Key On Engine Running (KOER) Self-Test. Key ON Engine Running (KOER) Self-Test

- Is Diagnostic Trouble Code (DTC) 136, 172, or 176 present?

Yes -- Remove jumper. Go to HB22. HB22 - HO2S Check

No -- Remove jumper. Reconnect HO2S. Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary. If OK, replace PCM. Drive vehicle 5 miles/55 mph. Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)