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Home >> Mazda >> 2003 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 26 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0031: Ho2S Heater (Front) Circuit Low >> Diagnosis & Repair Procedure

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 front HO2S 4-pin connector. Check for damaged or corroded front HO2S connector terminals. Repair as necessary, and go to step  8. If connector terminals are okay, go to next step.
  3. Measure resistance between front HO2S 4-pin connector terminals "C" and "D". See Fig 1. If resistance is about 5.6 ohms, go to next step. If resistance is not as specified, replace front HO2S and go to step  8.
    Fig 1: Identifying Front HO2S Connector Terminals
    G00143764Courtesy of MAZDA MOTORS CORP.
  4. Turn ignition switch to ON position. Measure voltage between ground and front HO2S 4-pin harness connector terminal "C" (Black/Blue wire). See Figure. If battery voltage is present, go to next step. If battery voltage is not present, check for open in circuit between ignition switch and front HO2S. See WIRING DIAGRAMS article. Go to step  8.
  5. Turn ignition switch off. Disconnect PCM 104-pin harness connector. See Fig 2. Check for damaged or corroded terminals. Repair as necessary, and go to step  8. If connector terminals are okay, go to next step.
    Fig 2: Identifying PCM 104-Pin Harness Connector
    G96F31315Courtesy of MAZDA MOTORS CORP.
  6. Check for continuity between ground and front HO2S 4-pin harness connector terminal "D" (Light Green/Red wire). See Figure. If continuity is not present, go to next step. If continuity is present, check for short to ground in Light Green/Red wire between front HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 94. See WIRING DIAGRAMS article. Go to step  8.
  7. Check for continuity between front HO2S 4-pin harness connector terminal "D" (Light Green/Red wire) and PCM harness connector terminal No. 94 (Light Green/Red wire). See Figure and Fig 2 . If continuity is present, go to next step. If continuity is not present, check for open in Light Green/Red wire between front HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 94. 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 P0031 is present, replace PCM and go to next step. If DTC P0031 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.
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