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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 P0138: Rear Ho2S Circuit - High 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. Verify Related Pending Or Stored DTCs -  Turn ignition off, then on (engine off). Verify pending code or stored DTCs using WDS or equivalent. If other DTC is present, go to appropriate DTC trouble shooting procedures. 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 is present on FREEZE FRAME DATA, go to next step. If any other DTC triggered FREEZE FRAME DATA, diagnose that DTC first. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  5. Inspect Rear HO2S Signal Circuit For Short To Power Supply Circuit -  Turn ignition off. Disconnect rear HO2S 4-pin harness connector. Turn ignition on, engine off. Measure voltage between rear HO2S 4-pin harness connector terminal "A" and body ground. See Figure. If any voltage is present, repair short to power supply circuit in White/Blue wire between rear HO2S 4-pin harness connector terminal "A" and PCM 30-pin harness connector terminal "1Y". 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 PID using WDS or equivalent. Verify PID while racing engine at least 10 times (in NEUTRAL (MTX) or PARK (ATX)). If PID reading does not stay at more than 0.45 volt, go to next step. If PID reading stays at more than 0.45 volt, repair or replace rear HO2S. After repair, go to next step.
  7. Verify Trouble Shooting Of DTC P0138 Completed -  Make sure to reconnect all disconnected connectors. Turn ignition on, engine off. Clear DTC from PCM memory using WDS or equivalent. Perform MODE 1 - PCM ADAPTIVE MEMORY PRODUCE DRIVE MODE  and MODE 3 - HO2S HEATER, HO2S & TWC REPAIR VERIFICATION DRIVE MODE  under DRIVE CYCLES. 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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