Diagnosis & Repair Procedure
WARNING: This page is about a different car, the 2002 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.
- Ensure FREEZE FRAME DATA has been recorded. Check for related service bulletins. Repair as necessary and go to next step.
- Perform KOER self-test. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. If DTC P1127 is present, go to appropriate test. If DTC P1127 is not present, go to next step.
- Turn ignition on. Using scan tool, access Generic OBD-II functions and enter. Select DIAGNOSTIC MONITORING TEST RESULTS and enter. Scroll to TEST ID: #10:03:01 and enter. Press START. If measured value is more than 461, go to step 8 . If measured value is 461 or less, front HO2S has failed test, go to next step.
- Check following possibilities as potential source of front HO2S contamination:
- Use of unapproved silicon sealers.
- Fuel contaminated by silicon additives.
- Excessive oil burning.
- Antifreeze leaking internally.
- Fuel contaminated by lead.
- Use of unapproved cleaners.
If any mentioned conditions are present, repair source of front HO2S contamination as necessary. Replace front HO2S. If none of the mentioned conditions are present, go to next step.
- Check the following as potential source of air leak:
- Leaking vacuum hoses connected to Mass Airflow (MAF) sensor.
- Leaking vacuum hoses connected to throttle body.
- Leaking intake manifold gasket.
- Disconnected PCV system.
- Other vacuum hoses disconnected.
- Poorly seated oil dipstick and/or dipstick tube.
- Exhaust leaks up stream of front HO2S.
- Turn ignition off. Disconnect scan tool and PCM connector. Check for damaged or corroded PCM connector terminals. Repair if necessary. Disconnect front HO2S connector. Measure resistance in Red wire between front HO2S harness connector terminal "A" and PCM harness connector terminal No. 60. See Fig 1 . On non-California emission equipped vehicles, also measure resistance between front HO2S harness connector terminal "A" (Red wire) and PCM harness connector terminal No. 35 (Yellow wire). On California emission equipped vehicles, also measure resistance between front HO2S body and ground. If any resistance measurement is 5 ohms or more, repair open circuit as necessary and go to step 8 . If all resistance measurements are less than 5 ohms, go to next step.
- Reconnect front HO2S connector. Measure resistance between PCM harness connector terminals No. 60 (Red wire) and No. 71 (Red/Black wire), terminals No. 60 (Red wire) and No. 97 (Red/Black wire), and between terminals No. 60 (Red wire) and No. 91 (Black/Yellow wire). See Fig 1 . If all measurements are more than 10 k/ohms, go to next step. If any measurement is 10 k/ohms or less, repair shorted circuit as necessary and go to next step.
- Reconnect all connections. Turn ignition on. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. Start engine. Using scan tool, access DIAGNOSIS MONITORING TEST RESULTS in GENERIC OBD II FUNCTIONS. Monitor TEST #10:02:11 (bank one voltage amplitude between rich and lean) and #10:03:01 (front HO2S switching point). If measured value is within specification, replace PCM and go to next step. See REMOVAL, OVERHAUL & INSTALLATION article. On vehicles equipped with immobilizer system, reprogram ignition key identification numbers. See COMPUTER RELEARN PROCEDURES - IMPORT article in GENERAL INFORMATION. If measured value is not within specification, go to next step.
- Perform DTC confirmation procedure. See DTC CONFIRMATION PROCEDURE under SELF-DIAGNOSTIC SYSTEM. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. If any other DTC is present, go to appropriate test.