Diagnostic Procedure

• Have the FREEZE FRAME DATA (Mode 2)/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS (engine cooling system related) been recorded?

• Verify related Service Bulletins and/or on-line repair information availability.
• Is any related repair information available?

• If the vehicle is not repaired, go to the next step.

• Switch the ignition to off, then to ON (engine off).
• Perform the Pending Trouble Code Access Procedure and DTC Reading Procedure.

  (See ON-BOARD DIAGNOSTIC TEST .)

• Are any other PENDING CODEs and/or DTCs present?

• Switch the ignition to off.
• Inspect the thermostat.

  (See THERMOSTAT INSPECTION .)

• Is there any malfunction?

• Inspect the ECT sensor.

  (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION .)

• Is there any malfunction?

• Make sure to reconnect all disconnected connectors.
• Cool down the engine.
  NOTE:

  • If workshop inside and outside temperature difference is significant, PCM might not operate thermostat monitor. Therefore, it is recommended to cool down engine out of workshop.
• Switch the ignition to ON (engine off).
• Clear the DTC from the PCM memory using the M-MDS.

  (See AFTER REPAIR PROCEDURE .)

• Access the ECT and IAT PIDs using the M-MDS under the following conditions:

  (See ON-BOARD DIAGNOSTIC TEST .)

  P0126:00 

  • IAT: above -10 °C {14 °F} 
  • P0128:00 

    IAT: above -10 °C {14 °F} 

  • ECT: below 36 °C {97 °F} 
  • Difference between ECT and IAT: below 6 °C {10.8 °F} 
• Is there any PID that out of the specification?

• Go to the next step.

P0128:00:

• Go to Step 8.

• Start the engine and turn off the electrical load and A/C.
• Access the TH_M (Temp unit) and TH_M_MIN (Temp unit) PIDs using the M-MDS.

  (See ON-BOARD DIAGNOSTIC TEST .)

  NOTE:

  • This test requires actual driving. Chassis roller 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 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 the TH_M and TH_M_MIN PIDs values.
• Is the TH_M value above TH_M_MIN value?

• Start the engine and turn off the electrical load and A/C.
• Access the TH_M (Temp and Num units), TH_M_MAX (Num unit) and TH_M_MIN (Temp unit) PIDs using the M-MDS.

  (See ON-BOARD DIAGNOSTIC TEST .)

  NOTE:

  • This test requires actual driving. Chassis roller cannot be used for this test.
  • During the test drive, constant speed should be maintained, although 2 or 3 stops (e.g. for traffic signals) is acceptable. Stop-and-go (e.g. in case of traffic congestion) is not acceptable during the test period.
• Verify the TH_M, TH_M_MAX and TH_M_MIN PIDs values.
• Are TH_M value of Num unit below TH_M_MAX value and TH_M value of Temp unit above TH_M_MIN value?

• If the malfunction recurs, replace the PCM.

  (See PCM REMOVAL/INSTALLATION .)

• Perform the "AFTER REPAIR PROCEDURE".

  (See AFTER REPAIR PROCEDURE .)

• Are any DTCs present?