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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 P0138 Or DTC P0158 >> 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. Verify Related Pending Code Or Stored DTCs -  Turn ignition off, then on (engine off). Verify pending code or stored DTCs using WDS or equivalent. If any other DTC is present, go to appropriate DTC trouble shooting procedure. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTCs are present, go to next step.
  4. Identify Trigger DTC For FREEZE FRAME DATA -  If DTC P0138 or P0158 are on FREEZE FRAME DATA, go to next step. If DTC P0138 or P0158 triggered FREEZE FRAME DATA, go to appropriate DTC trouble shooting procedure for DTC that triggered FREEZE FRAME DATA. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  5. Inspect HO2S (RR, LR) Signal Circuit For Short To Power -  Turn ignition off. Disconnect right rear HO2S for P0138 or left rear HO2S for P0158 4-pin harness connector. Turn ignition on, engine off. Measure voltage between following:
    • Right rear HO2S 4-pin harness connector terminal "A" (White wire) and body ground
    • Left rear HO2S 4-pin harness connector terminal "A" (Red wire) and body ground
    If voltage is not present, go to next step. If any voltage reading is present, repair suspected wire or replace wire harness. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. After repair, go to step  7.
  6. Verify Current Input Signal Status -  Start engine. Access O2S12 for P0138 or O2S22 for P0158 PID using WDS or equivalent. Verify PID while racing engine at least 10 times in Park (ATX) or Neutral (MTX). If PID reading does not stay at 0.45 volt or more, go to next step. If PID reading stays at 0.45 volt or more, replace suspected HO2S. After repair, go to next step.
  7. Verify Trouble Shooting Of DTC P0138 Or P0158 Is Completed -  Make sure to reconnect all disconnected connectors. Turn ignition on, engine off. Clear DTC from memory using WDS or equivalent. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Run MODE 1 - PCM ADAPTIVE MEMORY PRODUCE DRIVE MODE , MODE 2 - EGR SYSTEM REPAIR VERIFICATION DRIVE MODE  and MODE 3 - HO2S HEATER, HO2S & TWC REPAIR VERIFICATION DRIVE MODE  . 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.
  8. 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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