Diagnostic Procedures
- If QUICK TEST was not performed, go to QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If QUICK TEST was performed and KOEO DTC P0135, P0141, P0155 and P0161 were not present, fault may be intermittent. Refer to INTERMITTENT testing under SYSTEM TESTS . If same DTCs were present, go to next step.
- Visual Inspection
Visually inspect suspect HO2S circuit for exposed wiring, contamination, corrosion and proper assembly. If no concerns were found during visual inspection, go to next step. If any concerns were found during visual inspection, repair as necessary. After repair, go to step 8. - Check For VPWR At Vehicle Harness Connector
If DTCs P0135 and P0155, P0141 or P0161 are displayed, both heater circuits will require testing. DTCs displayed separately are tested individually. Disconnect appropriate HO2S 4-pin harness connector(s). Turn ignition on, engine off. Measure voltage between HO2S 4-pin harness connector(s) VPWR terminal (Light Blue/Orange wire) and SIG RTN terminal (Orange wire). If voltage reading is more than 10.5 volts, go to next step. If voltage reading is 10.5 volts or less, check No. 5 FUEL PUMP fuse (15-amp) in engine compartment fuse/relay box. If fuse is okay, repair open Light Blue/Orange between No. 5 FUEL PUMP fuse (15-amp) and suspect HO2S 4-pin harness connector. See WIRING DIAGRAMS article. After repair, go to step 8. - Check HO2S Heater Resistance
Disconnect suspect HO2S 4-pin harness connector. Measure resistance of HO2S HTR GND at component connector. For DTC P0135 (Red/White wire), P0141 (White/Black wire), P0155 (Yellow/Light Blue wire) or P0161 (Tan/Yellow wire). See Figure and Figure . If resistance reading is 3-30 ohms, go to next step. If resistance reading is not as specified, replace suspect HO2S. After repair, go to step 8. - Check For HTR GND & VPWR Shorted To HO2S Case
Measure resistance between HO2S HTR GND terminal at HO2S component connector and HO2S case. Measure resistance between HO2S HTR GND terminal and SIG RTN terminal (Orange wire) at HO2S component connector. Measure resistance between HO2S VPWR terminal (Light Blue/Orange wire) at HO2S component connector and HO2S case. If resistance readings are more than 10,000 ohms, go to next step. If resistance reading is 10,000 ohms or less, replace suspect HO2S. After repair, go to step 8. - Check For Shorts To Other Grounds & VPWR In HO2S HTR GND Harness Circuits
Disconnect scan tool from DLC. Disconnect PCM 104-pin harness connector. Connect Breakout Box (49-UN01-130) to PCM harness connector only. See Figure. Use list to measure resistance between appropriate breakout box terminals:- For DTC P0135, terminal No. 93 and terminals No. 71, 91 and 103.
- For DTC P0141, terminal No. 100 and terminals No. 71, 91 and 103.
- For DTC P0155, terminal No. 94 and terminals No. 71, 91 and 103.
- For DTC P0161, terminal No. 96 and terminals No. 71, 91 and 103.
If resistance reading is more than 10,000 ohms, go to next step. If resistance reading is 10,000 ohms or less, repair short circuit. See WIRING DIAGRAMS article. After repair, go to step 8.
- Check For Open HO2S HTR GND Harness Circuit
Use following list to measure resistance between appropriate breakout box (HTR GND) terminal and HO2S 4-pin harness connector HTR GND terminal:- For DTC P0135, breakout box terminal No. 93.
- For DTC P0141, breakout box terminal No. 100.
- For DTC P0155, breakout box terminal No. 94.
- For DTC P0161, breakout box terminal No. 96.
If resistance reading is less than 4.0 ohms, open, shorted or excessive resistance in HTR circuit in PCM. Replace PCM. After repair, go to next step. If resistance reading is 4.0 ohms or more, repair open or excessive resistance in HTR GND circuit. See WIRING DIAGRAMS article. After repair, go to next step.
- Verify Trouble Shooting Of DTCs Completed
Reconnect all disconnected connectors. Clear DTCs from PCM memory using scan tool. Perform QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If same DTC is present, replace faulty PCM. Repeat QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If same DTC is not present, go to applicable procedure for other DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are set, procedure is complete.