Diagnosis & Repair Procedure
- Turn ignition off. Connect scan tool to DLC-2. Turn ignition on, engine off. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Check service bulletins for repair information related to this DTC. If repair information is not available, go to next step. If repair information is available, perform diagnosis and repair as necessary. After repair, go to step 6.
- Turn ignition switch off and then start engine. Using scan tool, check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. If any other DTCs are present, go to appropriate test. If no other DTCs are present, go to next step.
- Inspect exhaust system for any leakage. If exhaust system is okay, go to next step. If problem is found, repair as necessary. After repair, go to step 6.
- Ensure both HO2Ss are installed correctly (tight). If no problem is found, go to next step. If problem is found, repair as necessary and go to step 6.
- Using scan tool, access O2S11 (front HO2S) and O2S12 (rear HO2S) PIDs. Drive vehicle for 10 minutes at 40-60 MPH to ensure Warm Up Three-Way Catalytic Converter (WU-TWC) reaches operating temperature. Let engine idle and record PIDs for one minute. Scan tool should display graphs for O2S11 and O2S12. See Fig 1 and Fig 2
. Count number of times graphline crosses below .5V line (inversion) for both front and rear HO2Ss. Divide number of inversions for front HO2S by number of inversions for rear HO2S for ratio data. If ratio is 2 or more or no rear HO2S inversions, WU-TWC converter is functioning properly. See Fig 1 and Fig 2
. Replace suspect HO2S, then go to next step. If ratio is less than 2, WU-TWC converter has deteriorated. See Fig 1 and Fig 3
. Replace WU-TWC converter. After repair, go to step 6.
Courtesy of MAZDA MOTORS CORP.
Courtesy of MAZDA MOTORS CORP.
Courtesy of MAZDA MOTORS CORP.
- Reconnect all connectors. Turn ignition switch on. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. Using scan tool, perform DRIVE MODE 1 - PCM ADAPTIVE MEMORY , DRIVE MODE 2 - EGR MONITOR REPAIR VERIFICATION and DRIVE MODE 3 - HO2S, HO2S HEATER & TWC REPAIR VERIFICATION
under SELF-DIAGNOSTIC SYSTEM. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. If DTC P0421 is present, replace PCM and go to next step. If DTC P0421 is not present, go to next step.
- Cycle ignition switch from off to on. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM. If no other DTCs are present, testing is complete. If any other DTC is present, go to applicable test and repair.