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HOMESERVICE MANUALSMAZDA1999626 ES, 2.5 D, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 432 (ON-BOARD DIAGNOSTIC (ENGINE CONTROL SYSTEM 13BMSP])DTC P0126DIAGNOSTIC PROCEDURE
1999 Mazda 626 ES, 2.5 D, Standard

Diagnostic procedure

1999 Mazda 626 ES, 2.5 D, StandardSECTION Diagnostic procedure
WARNING: This page is about a different car, the 2005 Mazda RX-8. However, it is still accessible from the selected car via links, so may be relevant.
DTC P0126 DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1 VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED 
  • Have FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (Thermostat 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 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.
3 VERIFY FOR OTHER STORED DTC 
  • Turn the ignition switch off, then to the ON position (Engine off).
  • Verify for the other stored DTCs.
  • Are other DTCs present?
 Yes Go to the appropriate DTC inspection.
(See DTC TABLE .)
No Go to the next step.
4 VERIFY CURRENT INPUT SIGNAL STATUS OF VSS 
  • Connect the WDS or equivalent to the DLC-2.
  • Start the engine.
  • Access the VSS PID.
  • Inspect the VSS PID. (See PCM INSPECTION .)
  • Is the PID normal?
 Yes Go to the next step.
No Inspect the malfunctioning part according to the inspection results.
Then go to Step 8.
5 INSPECT IAT SENSOR  Yes Replace the MAF/IAT sensor, then go to Step 8.
(See MASS AIR FLOW (MAF)/INTAKE AIR TEMPERATURE (IAT) SENSOR REMOVAL/INSTALLATION .)
No Go to the next step.
6 INSPECT ECT SENSOR  Yes Replace the ECT sensor, then go to Step 8.
(See ENGINE COOLANT TEMPERATURE (ECT) SENSOR REMOVAL/INSTALLATION .)
No Go to the next step.
7 INSPECT COOLANT THERMOSTAT  Yes Replace the coolant thermostat, then go to the next step.
(See THERMOSTAT REMOVAL/INSTALLATION .)
No Go to the next step.
8 VERIFY MONITORING CONDITION FOR REPAIR VERIFICATION 
  • Leave the vehicle in a place that is at a temperature of approx. 25 °C {77 °F}  for more than 6 hours. 
  • Make sure to reconnect all disconnected connectors.
  • Clear the DTC from the PCM memory using the WDS or equivalent.
  • Access the ECT and IAT PIDs.
  • Verify that each PID is within following specifications.
    • IAT: more than -10 °C {14 °F} 
    • ECT: less than 51 °C {123 °F} 
  • Are the ECT and IAT PIDs normal?
 Yes Go to the next step.
No Inspect the malfunctioning part according to inspection the results.
Then repeat this step.
9 VERIFY TROUBLESHOOTING OF DTC P0126 COMPLETED 
  • Connect the WDS or equivalent to the DLC-2.
  • Start the engine.
  • Verify that the E/L and A/C are off.
  • Access the DIAGNOSTIC MONITORING TEST RESULTS.
  • Monitor the TEST #10:E1:81 (ECT).
    NOTE:
    • This test requires actual driving. Chassis dynamometer cannot be used for this test.
    • During the test drive, constant speed should be maintained, although 2 or 3 stops during every 5 min of driving time (e.g. for traffic signals) is acceptable. Stop-and-go (e.g. in case of traffic congestion) is not acceptable during the test period.
    • Test period depends on ECT at the engine start, (e.g. if ECT is -10 °C {14 °F}, monitoring period is 38 min and ECT is 30 °C {86 °F}, monitoring period is 8 min)
  • Verify TEST #10:E1:81 (ECT) value.
  • Is value above minimum value?
 Yes Go to the next step.
No Replace the PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION .)
10 VERIFY AFTER REPAIR PROCEDURE  Yes Go to the applicable DTC inspection.
(See DTC TABLE .)
No DTC troubleshooting completed.
RENDER: 1.0x

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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.