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Diagnosis & Repair Procedure

WARNING: This page is about a different car, the 2002 Mazda Protege5 and 2002 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ensure FREEZE FRAME DATA has been recorded. Check for related service bulletins. Repair as necessary and go to next step.
  2. Turn ignition switch off. Disconnect rear HO2S 4-pin connector. Check for damaged or corroded rear HO2S connector terminals. Repair as necessary, and go to step  8. If connector terminals are okay, go to next step.
  3. Measure resistance between rear HO2S 4-pin connector terminals "C" and "D". See Fig 1. If resistance is 15.7 ohms, go to next step. If resistance is not as specified, replace rear HO2S and go to step  8.
    Fig 1: Identifying Rear HO2S Connector Terminals
    G00143765Courtesy of MAZDA MOTORS CORP.
  4. Turn ignition switch on. Measure voltage between ground and rear HO2S 4-pin harness connector terminal "C" (Black/Blue wire). See Fig 2. If battery voltage is present, go to next step. If battery voltage is not present, check for open in circuit between ignition switch and rear HO2S. See WIRING DIAGRAMS article. Go to step  8.
  5. Turn ignition switch off. Disconnect PCM 104-pin harness connector. See Figure. Check for damaged or corroded PCM connector terminals. Repair as necessary, and go to step  8. If connector terminals are okay, go to next step.
  6. Check for continuity between ground and rear HO2S harness connector terminal "D" (Green/Red wire). See Fig 2. If continuity is not present, go to next step. If continuity is present, check for short to ground in Green/Red wire between rear HO2S and PCM connector terminal No. 93. See WIRING DIAGRAMS article. Go to step  8
  7. Check for continuity of Green/Red wire between rear HO2S harness connector terminal "D" and PCM harness connector terminal No. 93. See Fig 2 and Figure . If continuity is present, go to next step. If continuity is not present, repair open in Green/Red wire. See WIRING DIAGRAMS article. Go to next step.
  8. Reconnect all connectors. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine and allow it to reach normal operating temperature. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P0037 is present, replace PCM and go to next step. If DTC P0037 is not present, go to next step.
  9. 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.
Fig 2: Identifying Wire Side Of HO2S Harness Connector Terminals
G00032517Courtesy of MAZDA MOTORS CORP.
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