Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed through wire insulation or a broken wire inside insulation. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness.

Using scan tool, monitor signal voltage while wiggling HO2S related connectors and wiring harness with a warm engine running at part throttle in closed loop. If a failure is induced, signal voltage will change from normal fluctuating voltage to a fixed voltage. A change in voltage will assist in isolating location of fault. DO NOT  solder HO2S wires.

1. Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
2. Start engine and allow it to reach normal operating temperature. Apply parking brake and increase engine speed to greater than 1200 RPM for 2 minutes. Using scan tool, observe HO2S No. 1, bank 1 parameter. If reading varies outside 400-500 mV range, turn engine off and go to next step. If reading does not vary outside 400-500 mV range, go to step 4).
3. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. If DTC P0134 is set, go to next step. If DTC P0134 is not set, check for an intermittent problem, see DIAGNOSTIC AIDS  .
4. Inspect sensor harness for damage. Repair as necessary. If harness is okay, go to next step.
5. Check for poor signal circuit (Blue and Pink wires - 3.2L; Green and Red wires - 3.5L) connection at HO2S No. 1, bank 1 harness connector. Repair as necessary. Retest system. If connection is okay, go to next step.
6. Check for poor HO2S No. 1, bank 1 signal circuit (Blue and Pink wires - 3.2L; Green and Red wires - 3.5L) connections at PCM harness connectors. Repair as necessary. Retest system. If connections are okay, go to next step.
7. Turn ignition off. Disconnect PCM connectors. Measure resistance of HO2S No. 1, bank 1 high signal circuit (Pink wire - 3.2L; Red wire - 3.5L) between PCM and HO2S. If resistance is greater than 5 ohms, repair open or poor connection. Retest system. If wire is okay, go to next step.
8. Measure resistance of HO2S No. 1, bank 1 low signal circuit (Blue wire - 3.2L; Green wire - 3.5L) between PCM and HO2S. If resistance is greater than 5 ohms, repair open or poor connection. Retest system. If wire is okay, reconnect PCM connectors and go to next step.
9. Disconnect HO2S No. 1, bank 1 connector. Turn ignition on. Using a fused jumper wire, connect high and low signal circuits (Blue and Pink wires - 3.2L; Green and Red wires - 3.5L) of HO2S No. 1, bank 1 (PCM side) to ground. If scan tool display is 0-10 mV, replace HO2S No. 1, bank 1. If display is not as specified, replace PCM. Retest system.