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HOMESERVICE MANUALSMAZDA2008CX-7 TOURING, 2.3 3, AWDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISON-BOARD DIAGNOSTIC (ENGINE CONTROL SYSTEM) - (3 OF 5)DTC P0138[L3 WITH TC]DIAGNOSTIC PROCEDURE
2008 Mazda CX-7 Touring, 2.3 3, AWD

Diagnostic procedure

2008 Mazda CX-7 Touring, 2.3 3, AWDSECTION Diagnostic procedure
DTC P0138[L3 WITH TC] DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1 VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED 
  • Have the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (HO2S related) been recorded?
 Yes Go to the next step.
No Record the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.
2 VERIFY RELATED SERVICE INFORMATION AVAILABILITY 
  • Verify related service bulletins and/or repair Information availability.
  • Is any related Service Information available?
 Yes Perform the repair or diagnosis according to available Service Information.
  • If vehicle is not repaired, go to the next step.
No Go to the next step.
3 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[L3 WITH TC] .)
No Go to the next step.
4 IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA 
  • Is DTC P0138 on FREEZE FRAME DATA?
 Yes Go to the next step.
No Go to the troubleshooting procedures for the DTC on the FREEZE FRAME DATA. (See DTC TABLE[L3 WITH TC] .)
5 INSPECT REAR HO2S SIGNAL CIRCUIT FOR SHORT TO POWER SUPPLY 
  • Turn the ignition switch off.
  • Disconnect rear HO2S connector.
  • Turn the ignition switch to the ON position. (Engine off)
  • Measure the voltage between rear HO2S terminal A (wiring harness-side) and body ground.
  • Is there any voltage?
 Yes Replace short to power supply, then go to Step 7.
No Go to the next step.
6 VERIFY CURRENT INPUT SIGNAL STATUS 
  • Start the engine.
  • Access the O2S12 PID using the M-MDS.
  • Verify the PID while racing the engine at least 10 times  in NEUTRAL.
  • Does the PID stay above 0.55 V?
 Yes Replace the sensor, then go to the next step. (See EXHAUST SYSTEM REMOVAL/INSTALLATION[L3 WITH TC] ).
No Go to the next step.
7 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.
  • Run the PCM adaptive memory procedure drive mode and HO2S heater, HO2S, and TWC repair verification drive mode.

    (See OBD-II DRIVE MODE[L3 WITH TC] .)

  • Is the PENDING CODE for this DTC present?
 Yes Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION[L3 WITH TC] ).
No Go to the next step.
8 VERIFY AFTER REPAIR PROCEDURE 
 Yes Go to the applicable DTC troubleshooting. (See DTC TABLE[L3 WITH TC] .)
No Troubleshooting completed.
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.