Diagnostic Procedures
WARNING: This page is about a different car, the 2003 Mazda Tribute. However, it is still accessible from the selected car via links, so may be relevant.
- If QUICK TEST was not performed, go to QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If QUICK TEST was performed, go to next step.
- Check For Source Of Potential HO2S Contamination -
Investigate following items as potential sources of HO2S contamination:
- Engine coolant leaking internally in the engine.
- Excessive oil burning (i.e., rings, valve seals and/or oil overfill).
- Fuel contaminated with silicone additives.
- Lead contaminated fuel.
- Short drive cycles in cold weather.
- Use of unapproved cleaning agents.
- Use of unapproved silicone sealers.
- Check For Unmetered Air Leaks -
Fuel calculations can be affected by unmetered air leaks. Carefully inspect the following areas for potential air leaks:
- Exhaust leaks at flanges and gaskets.
- Hoses connecting MAF/IAT sensor assembly.
- Hoses connecting to throttle body.
- Improperly seated dipstick tube and oil filler cap.
- Intake manifold gasket leaks.
- PCV disconnected.
- Vacuum lines disconnected.
- Check HO2S Circuit Wiring With PCM Connected - Connect scan tool to DLC. Disconnect suspect HO2S 4-pin harness connector. Connect fused jumper wire between HO2S 4-pin harness connector HO2S SIG terminal and VPWR terminal. Turn ignition on, engine off. Access O2S11 for P0133 or O2S21 for P0153 and note voltage reading. If voltage reading is more than 1.5 volts, go to next step. If voltage reading is 1.5 volts or less, remove fused jumper wire and go to step 6.
- Check For Short To VPWR And VREF - Disconnect scan tool from DLC. Turn ignition on, engine off. Measure voltage between suspect HO2S 4-pin harness connector HO2S SIG terminal and SIG RTN terminal. If voltage reading is less than 4.5 volts, replace HO2S and change oil and filter. For HO2S locations see Figure. After repair, go to step 8. If voltage reading is 4.5 volts or less, repair short in VPWR or VREF circuit. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step 8.
- Check Resistance Of HO2S Signal Circuit - Disconnect PCM 104-pin harness connector. Connect Breakout Box (49-UN01-130) to PCM harness connector only. See Figure. Measure resistance of the HO2S SIG circuit between breakout box terminal No. 60 (DTC P0133) or No. 87 (DTC P0153) and HO2S 4-pin harness connector. See Figure. Record measurement. Measure resistance of SIG RTN circuit (Orange wire) between breakout box terminal No. 91 and HO2S 4-pin harness connector. Record measurement. If each resistance reading is less than 5 ohms, go to next step. If each resistance reading is 5 ohms or more, repair open circuit. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step 8.
- Check For Short To Ground -
Disconnect scan tool from DLC. For P0133 or P0138 (Front), measure resistance between breakout box terminals:
- No. 60 (HO2S SIG) and No. 91 (SIG RTN) for sensor ground.
- No. 60 (HO2S SIG) and No. 71 (PWR GND).
For P0152 or P0153 (Front), measure resistance between breakout box terminals:
- No. 87 (HO2S SIG) and No. 91 (SIG RTN) for sensor ground.
- No. 87 (HO2S SIG) and No. 71 (PWR GND).
- Drive Cycle - Reconnect all disconnected connectors. Clear DTCs from PCM memory using scan tool. Perform Fuel Monitor or HO2S Monitor Drive Cycle. Refer to HO2S MONITOR REPAIR VERIFICATION DRIVE CYCLE or FUEL OR MISFIRE MONITOR REPAIR VERIFICATION DRIVE CYCLE under MONITOR REPAIR VERIFICATION DRIVE CYCLES. Retrieve pending code. If same DTC is present, replace PCM. After repair, go to next step. If same DTC is not present, go to next step.
- Verify Trouble Shooting Of DTCs Completed - Perform QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If any DTC is present, go to applicable procedure for other DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are set, trouble shooting is complete.