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Home >> Mazda >> 2003 >> Tribute LX, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 61 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0138: Ho2S (Rear) Circuit - High Input >> Diagnostic Procedure

Diagnostic Procedure

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  1. Verify Related Repair Information Availability -  Turn ignition off. Connect scan tool to DLC-2. Turn ignition on, engine off. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Check service bulletins for repair information related to this DTC. If repair information is not available, go to next step. If repair information is available, perform diagnosis and repair as necessary. After repair, go to next step.
  2. Verify Related Pending & Stored DTCs -  Turn ignition off, then start engine. Using scan tool, check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If no other DTCs related to P0138 are present, go to next step. If any other related DTCs are present, go to appropriate trouble shooting procedure. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  3. Identify Trigger DTC For Freeze Frame Data -  Check if DTC P0138 is present in FREEZE FRAME DATA. If DTC P0138 is present, go to next step. If any other DTC is present that triggered freeze frame data, go to appropriate DTC trouble shooting procedure. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  4. Inspect HO2S (Rear) 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 ground and rear HO2S 4-pin harness connector terminal "A" (Yellow/Blue wire). If voltage is not present, go to next step. If any voltage is present, repair short circuit to power in Yellow/Blue wire between rear HO2S 4-pin harness connector terminal "A" and PCM 104-pin harness connector terminal No. 35. See Figure and Fig 1 . See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, go to step  6.
  5. Verify Current Input Signal Status -  Start engine. Using scan tool, access O2S12 PID data. Race engine at least 10 times in neutral. If O2S12 PID reading stays at more than .45 volt, replace rear HO2S. After repair, go to next step. If O2S12 PID reading does not stay at more than .45 volt, go to next step.
  6. Verify Trouble Shooting Of DTC P0138 Completed -  Reconnect all connectors. Turn ignition on, engine off. Clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Perform MODE 1 - PCM ADAPTIVE MEMORY PROCEDURE DRIVE MODE  and MODE 3 - HO2S, HO2S HEATER & TWC REPAIR VERIFICATION DRIVE MODE  . Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P0138 is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION article. After repair, go to next step. If same DTC P0138 is not present, go to next step.
  7. 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, follow appropriate DTC diagnostic procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
Fig 1: Identifying Rear HO2S 4-Pin Harness Connector Terminals
G00143768Courtesy of MAZDA MOTORS CORP.
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