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Home >> Mazda >> 2002 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 60 (Engine Controls [Self-Diagnostics 2.3L]) >> Diagnostic Tests >> DTC P0031: 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 Front HO2S Connector For Poor Connection -  Turn ignition off. Disconnect front HO2S 4-pin harness connector. Inspect for poor connection (such as damaged, pulled-out pins, corrosion). If any malfunctions are present, repair or replace terminal. After repair, go to step  9. If malfunctions are not found, go to next step.
  4. Inspect Front HO2S Heater -  Inspect front HO2S heater. See HEATED OXYGEN SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - MAZDA6, MIATA, MPV, PROTEGE & PROTEGE5 article. If front HO2S heater is okay, go to next step. If front HO2S heater is not okay, replace front HO2S. After repair, go to step  9.
  5. Inspect Power Circuit Of Front HO2S Heater For Open Circuit -  Turn ignition on, engine off. Measure voltage in White/Red wire between front HO2S 4-pin harness connector terminal "C" and body ground. See Fig 1. If battery voltage is present, go to next step. If battery voltage is not present, repair or replace harness for open circuit in White/Red wire between main relay (inside engine fuse/relay box) and HO2S 4-pin harness connector terminal "C". See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair, go to step  9.
    Fig 1: Identifying Front HO2S Heater Circuit & Harness Connector Terminals
    G00193652Courtesy of MAZDA MOTORS CORP.
  6. Inspect PCM Connector For Poor Connection -  Turn ignition off. Disconnect PCM connectors. Inspect for poor connection (such as damaged, pulled-out pins, corrosion). If no malfunctions are present, go to next step. If any malfunctions are present, repair terminal. After repair, go to step  9.
  7. Inspect Control Circuit Of Front HO2S Heater For Short To Ground -  Check for continuity between front HO2S 4-pin harness connector terminal "D" and body ground. If continuity is not present, go to next step. If continuity is present, repair or replace wire harness for short circuit to ground. After repair, go to step  9.
  8. Inspect Control Circuit Of Front HO2S Heater For Open Circuit -  Check for continuity in White/Black wire between front HO2S 4-pin harness connector terminal "D" and PCM 30-pin harness connector terminal "4A". If continuity is present, go to next step. If continuity is not present, repair or replace wire harness for open circuit in White/Black wire between front HO2S 4-pin harness connector terminal "D" and PCM 30-pin harness connector terminal "4A". See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair, go to next step.
  9. Verify Trouble Shooting Of DTC P0031 Is Completed -  Make sure to reconnect all disconnected connectors. Clear DTC from PCM memory using WDS or equivalent. Turn ignition off. Start engine and warm it up completely. If PENDING CODE of same DTC is not present, go to next step. If PENDING CODE of 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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