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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 61 (Engine Controls [Self-Diagnostics 3.0L]) >> Diagnostic Tests >> DTC P0051: Left Front Ho2S Heater Circuit - Low Input >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
  1. If FREEZE FRAME DATA has been recorded, go to next step. If FREEZE FRAME DATA has not been recorded, record FREEZE FRAME DATA. Go to next step.
  2. Verify Related Repair Information Availability -  Check for related Service Bulletins and/or on-line repair information availability. If any related repair information is available, perform repair or diagnosis according to available repair information. If vehicle is not repaired, go to next step. If related repair information is not available, go to next step.
  3. Inspect Left Front HO2S Connector For Poor Connection -  Turn ignition off. Disconnect left front HO2S 4-pin harness connector. Check for poor connection (such as damaged, pulled-out pins, and corrosion). If no malfunction is present, go to next step. If any malfunction is present, repair or replace terminal. After repair, go to step  9.
  4. Inspect Left Front HO2S Heater Power Circuit For Open Circuit -  Turn ignition on, engine off. Measure voltage between left front HO2S 4-pin harness connector terminal "C" (Blue/Black wire) and body ground. See Fig 1. If battery voltage is present go to next step. If battery voltage is not present, repair open circuit in Blue/Black wire between left front HO2S 4-pin harness connector terminal "C" and ignition relay harness connector or replace wire harness. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair, go to step  9.
    Fig 1: Identifying Left Front HO2S Circuits & Harness Connector Terminals
    G00221538Courtesy of MAZDA MOTORS CORP.
  5. Inspect Left Front HO2S Heater Control Circuit For Short To Ground -  Turn ignition off. Check for continuity between left front HO2S 4-pin harness connector terminal "D" (White/Green wire) and body ground. If continuity is not present, go to next step. If continuity is present, repair short circuit to ground in White/Green wire between left front HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 94 or replace wire harness. After repair, go to step  9.
  6. Inspect Left Front HO2S Heater -  Inspect left front HO2S heater. Refer to HEATED OXYGEN SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. If left front HO2S heater is okay, go to next step. If left front HO2S heater is faulty, replace left front HO2S. After repair, go to step  9.
  7. Inspect PCM Connector For Poor Connection -  Turn ignition off. Disconnect PCM 104-pin harness connector. Check for poor connection (such as damaged, pulled-out pins, and corrosion). If no malfunction is present, go to next step. If any malfunction is present, repair or replace terminal. After repair, go to step  9.
  8. Inspect Left Front HO2S Heater Control Circuit For Open Circuit -  Turn ignition off. Check for continuity between left front HO2S 4-pin harness connector terminal "D" (White/Green wire) and PCM 104-pin harness connector terminal No. 94. See Fig 1. If continuity is present, go to next step. If continuity is not present, repair open circuit in White/Green wire between left front HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 94 or replace wire harness. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair, go to next step.
  9. Verify Trouble Shooting Of DTC P0051 Is Completed -  Make sure to reconnect all disconnected connectors. Clear DTC from PCM memory using WDS or equivalent. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Turn ignition off. Start engine and warm it up completely. If PENDING CODE for same DTC is not present, go to next step. If PENDING CODE for same DTC is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION article. After repair, go to next step.
  10. Verify After Repair Procedure -  Using scan tool, perform After Repair Procedure. See AFTER REPAIR PROCEDURE . If any DTCs are present, go to appropriate DTC inspection. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are present, trouble shooting is complete.
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