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Home >> Mazda >> 2010 >> 5 Touring, 2.3 L >> Repair and Diagnosis >> Engine Performance >> System >> On-Board Diagnostic [Engine Control System L3] >> DTC P0138 >> Diagnostic procedure
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Diagnostic procedure

DTC P0138 [L3] DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1 IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA (MODE 2) 
  • Is DTC P0138 on FREEZE FRAME DATA (Mode 2)?
 Yes Go to the next step.
No Go to troubleshooting for DTC on FREEZE FRAME DATA (Mode 2).
(See DTC TABLE .)
2 VERIFY FREEZE FRAME DATA (MODE 12) AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED 
  • Have FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS (A/F sensor, HO2S related) been recorded?
 Yes Go to the next step.
No Record the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS on repair order, then go to the next step.
3 VERIFY RELATED REPAIR INFORMATION AVAILABILITY 
  • Verify related Service Bulletins and/or on-line repair information availability.
  • Is any related repair information available?
 Yes Perform repair or diagnosis according to the available \ repair information.
  • If the vehicle is not repaired, go to the next step.
No Go to the next step.
4 VERIFY RELATED PENDING OR STORED DTC 
  • Turn the ignition switch off, then to the ON position. (Engine off)
  • Verify pending code or stored DTCs using M-MDS.
  • Is other DTC present?
 Yes Go to the appropriate DTC troubleshooting procedures. (See DTC TABLE .)
No Go to the next step.
5 INSPECT HO2S TERMINALS 
  • Turn the ignition switch off.
  • Disconnect the HO2S sensor connector.
  • Inspect for poor connection (such as damaged/pulled-out pins, corrosion).
  • Is there any malfunction?
 Yes Repair or replace the terminal, then go to Step 10.
No Go to the next step.
6 INSPECT PCM TERMINAL 
  • Disconnect the PCM connector.
  • Inspect for poor connection (such as damaged/pulled-out pins, corrosion).
  • Is there any malfunction?
 Yes Repair the terminal, then go to Step 10.
No Go to the next step.
7 INSPECT HO2S CIRCUIT FOR SHORT TO WIRING HARNESSES 
  • HO2S and PCM connectors are disconnected.
  • Turn the ignition switch to off.
  • Inspect for continuity between HO2S sensor terminal A and B (wiring harness-side).
  • Is there continuity?
 Yes Repair or replace the wiring harness for a short, then go to Step 10.
No Go to the next step.
8 INSPECT HO2S SIGNAL CIRCUIT FOR SHORT TO POWER SUPPLY 
  • HO2S and PCM connectors are disconnected.
  • Turn the ignition switch to the ON position. (Engine off)
  • Measure the voltage between HO2S terminal A (wiring-harness-side) and body ground.
  • Is there any voltage?
 Yes Replace short to power supply, then go to Step 10.
No Go to the next step.
9 INSPECT THE HO2S 
 Yes Replace the HO2S, then go to the next step.
(See AIR FUEL RATIO (A/F) SENSOR, HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION .)
No Go to the next step.
10 VERIFY TROUBLESHOOTING OF DTC P0138 COMPLETED 
  • Make sure to reconnect all disconnected connectors.
  • Turn the ignition switch to the ON position. (Engine off)
  • Clear the DTC from the memory using the M-MDS.
  • Perform the KOEO self-test with M-MDS, or the "A/F sensor heater, HO2S heater", A/F sensor, HO2S, and TWC repair verification drive mode.

    (See KOEO/KOER SELF TEST .)

    (See OBD-II DRIVE MODE .)

  • Is the PENDING CODE for this DTC present?
 Yes Replace the PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION .)
No Go to the next step.
11 VERIFY AFTER REPAIR PROCEDURE 
 Yes Go to the applicable DTC troubleshooting.
(See DTC TABLE .)
No Troubleshooting completed.
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