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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 59 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0051: Left Front Ho2S Heater Circuit Low >> Diagnostic Procedures

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. Inspect Poor Connection Of HO2S (Left Front) Connector -  Turn ignition off. Disconnect left front HO2S 4-pin harness connector. Check for damaged, loose or corroded terminals. If problem is not present, go to next step. If problem is present, repair as necessary. After repair, go to step  8.
  3. Inspect HO2S Heater (Left Front) -  Measure resistance between left front HO2S terminals "C" and "D". See Figure. If resistance is 5.0-6.8 ohms, go to next step. If resistance is not 5.0-6.8 ohms, replace left front HO2S. After repair, go to step  8.
  4. Inspect HO2S Heater (Left Front) Power Circuit For Open -  Turn ignition on, engine off. Measure voltage in Black/White wire between ground and left front HO2S 4-pin harness connector terminal "C". If battery voltage is present, go to next step. If battery voltage is not present, repair open circuit in Black/White wire between left front HO2S 4-pin harness connector terminal "C" and ignition switch. See appropriate wiring diagram under ENGINE PERFORMANCE in WIRING DIAGRAMS. After repair, go to step  8.
  5. Inspect Poor Connection Of PCM Connector -  Turn ignition off. Disconnect PCM 104-pin harness connector. Check for damaged, loose or corroded terminals. If problem is not present, go to next step. If problem is present, repair as necessary. After repair, go to step  8.
  6. Inspect HO2S Heater (Left Front) Control Circuit For Short To Ground -  Check continuity in Orange wire between ground and left front HO2S 4-pin harness connector terminal "D". If continuity is not present, go to next step. If continuity is present, repair short to ground in Orange wire between left front HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 94. See Figure. After repair, go to step  8.
  7. Inspect HO2S Heater (Left Front) Control Circuit For Open -  Connect 104-pin Breakout Box (49-UN01-130) to PCM harness connector only. See Figure. Check continuity in Orange wire between left front HO2S 4-pin harness connector terminal "D" and breakout box terminal No. 94. If continuity is present, go to next step. If continuity is not present, repair open in Orange wire between left front HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 94. See Figure. After repair, go to next step.
  8. Verify Trouble Shooting Of DTC P0051 Completed -  Reconnect all connectors. Turn ignition on, engine off. Using scan tool, clear DTC from memory. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P0051 is not present, go to next step. If DTC P0051 is present, replace PCM. After repair, go to next step.
  9. 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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