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Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Mazda MPV and 2002 Mazda MPV. However, it is still accessible from the selected car via links, so may be relevant.
  1. Record freeze frame data. Check for service bulletins and on-line information. Repair as necessary. After repair, go to next step.
  2. Verify Related Pending Or Stored DTCs -  Turn ignition off, then on (engine off). Verify pending or stored DTCs. If no other DTCs are present, go to next step. If other DTCs are present, diagnose and repair first. Refer to DIAGNOSTIC TROUBLE CODE IDENTIFICATION .
  3. Identify Trigger DTC For FREEZE FRAME DATA -  Verify if DTC P0138 or P0158 are present on FREEZE FRAME PID data. If either DTC is present, go to next step. If either DTC is not present on FREEZE FRAME DATA, go to trouble shooting procedure for DTC that triggered FREEZE FRAME DATA. Refer to DIAGNOSTIC TROUBLE CODE IDENTIFICATION .
  4. Inspect HO2S (Rear) Signal Circuit For Short To Power Supply Circuit -  Turn ignition off. Disconnect right rear HO2S 4-pin harness connector (P0138) or left rear HO2S 4-pin harness connector (P0158). Turn ignition on, engine off. Check voltage between ground and appropriate rear HO2S 4-pin harness connector terminal "A". See Figure. If no voltage is present, go to next step. If voltage is present, repair short to power in circuit between:
    • Right rear HO2S 4-pin harness connector terminal "A" and PCM 104-pin harness connector terminal No. 35 (Green wire).
    • Left rear HO2S 4-pin harness connector terminal "A" and PCM 104-pin harness connector terminal No. 61 (Light Green wire).

    Repair as necessary. See appropriate wiring diagram under ENGINE PERFORMANCE in WIRING DIAGRAMS. After repair, go to step  6.

  5. Verify Current Input Signal Status -  Reconnect rear HO2Ss. Start engine. Using scan tool, access O2S12 (P0138) or O2S22 (P0158). Monitor PID reading while racing engine at least 10 times in park or neutral. If PID reading stays at more than .45 volt, replace suspect rear HO2S. After repair, go to next step. If PID reading is not as specified, go to next step.
  6. Verify Trouble Shooting Of DTC P0138 Or P0158 Completed -  Reconnect all components. Turn ignition on, engine off. Using scan tool, clear DTC. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine and perform MODE 1 - PCM ADAPTIVE MEMORY PRODUCE DRIVE MODE  and MODE 3 - HO2S HEATER, HO2S & TWC REPAIR VERIFICATION DRIVE MODE  under DRIVE MODES. Recheck for DTCs. If DTC P0138 or P0158 is present, replace PCM. After repair, go to next step. If DTC P0138 or P0158 is not present, go to next step.
  7. Verify After Repair Procedure -  Using scan tool, perform After Repair Procedure. See AFTER REPAIR PROCEDURE . If no other DTCs are present, testing is complete. If any other DTC is present, go to applicable test and repair.
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