DTC P0126:00, P0128:00 [L3 Turbo]SM2444170
DTC P0126:00, P0128:00 [L3 Turbo]

id0102b7900800

DTC P0126:00

DTC P0128:00

Coolant thermostat stuck open
DETECTION CONDITION
DTC P0126:00
• If the ECT signal never exceeds 71 °C {160 °F} after engine start for specified period, the PCM determines that the coolant thermostat is stuck open.
MONITORING CONDITIONS
― IAT: above -10 °C {14 °F}
― Vehicle speed: over 6 km/h {3.7 mph}
― Absolute load: above 10%
DTC P0128:00
• The PCM monitors MAF, IAT, VSS and ECT signals and calculate radiator heat radiation ratio while following monitoring conditions are met. If calculated value exceeds threshold, the PCM determines that the coolant thermostat is stuck open.
MONITORING CONDITIONS
― ECT at engine start: below 36 °C {97 °F}
― IAT: above -10 °C {14 °F}
― Difference between ECT at engine start and minimum IAT: below 6 °C {10.8 °F}
― Vehicle speed: over 30 km/h {18.6 mph}
Diagnostic support note
• This is an intermittent monitor (engine cooling system).
• The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
• PENDING CODE is available if the PCM detects the above malfunction condition during the first drive cycle.
• FREEZE FRAME DATA (Mode 2)/Snapshot data is available.
• DTCs are stored in the PCM memory.
POSSIBLE CAUSE
• Coolant thermostat malfunction
• ECT sensor malfunction
• Cooling system malfunction
• PCM malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION
1
VERIFY FREEZE FRAME DATA (MODE 2)/SNAPSHOT DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED
• Have the snapshot data and DIAGNOSTIC MONITORING TEST RESULTS (engine cooling system related) been recorded?
Yes
Go to the next step.
No
Record the FREEZE FRAME DATA (Mode 2)/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS on repair order, then go to the next step.
2
VERIFY RELATED SERVICE INFORMATION AVAILABILITY
• Verify related Service Information availability.
• Is any related Service Information available?
Yes
Perform repair or diagnosis according to the available Service Information.
• If the vehicle is not repaired, go to the next step.
No
Go to the next step.
3
VERIFY RELATED PENDING CODE AND STORED DTC
• Turn the ignition switch off, then to the ON position (engine off).
• Perform the DTC Reading Procedure and Pending Trouble Code Access Procedure. (See ON-BOARD DIAGNOSTIC TEST [L3 Turbo].)
• Are any other DTCs present?
Yes
Go to the applicable DTC inspection.
(See DTC TABLE [L3 Turbo].)
No
Go to the next step.
4
INSPECT COOLANT THERMOSTAT FOR WHETHER STUCK OPEN
• Inspect the coolant thermostat. (See THERMOSTAT INSPECTION [L3 Turbo].)
• Is there any malfunction?
Yes
Replace the coolant thermostat, then go to the next step.
(See THERMOSTAT REMOVAL/INSTALLATION [L3 Turbo].)
No
Inspect the ECT sensor.
(See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION [L3 Turbo].)
Replace the ECT sensor if necessary, then go to the next step.
(See ENGINE COOLANT TEMPERATURE (ECT) SENSOR REMOVAL/INSTALLATION [L3 Turbo].)
5
VERIFY MONITORING CONDITION FOR REPAIR VERIFICATION
• Make sure to reconnect all disconnected connectors.
• Cool down the engine.
Note
• If workshop inside and outside temperature difference is significant, the PCM might not operate thermostat monitor. Therefore, it is recommended to cool down the engine out of workshop.
• Turn the ignition switch to the ON position (engine off).
• Clear the DTC from the PCM memory using the M-MDS. (See AFTER REPAIR PROCEDURE [L3 Turbo].)
• Access the ECT, IAT PIDs and make sure that each value is within following specifications. (See ON-BOARD DIAGNOSTIC TEST [L3 Turbo].)
― ECT: below 36 °C {97 °F} (for P0128:00 only)
― IAT: above -10 °C {14 °F}
― Difference between ECT and IAT: below 6 °C {10.8 °F}(for P0128:00 only)
• Is there any PID that is out of specification?
Yes
Take corrective action (e.g. cool down the engine), then repeat this step.
No
DTC P0126:00:
• Go to the next step.
DTC P0128:00:
• Go to Step 7.
6
VERIFY TROUBLESHOOTING OF DTC P0126:00 COMPLETED
• Start the engine and turn off E/L and A/C.
• Access the PIDs TH_M (Temp unit) and TH_M_MIN (Temp unit) using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [L3 Turbo].)
Note
• This test requires actual driving. Chassis roller cannot be used for this test.
• During 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 the PIDs TH_M and TH_M_MIN values.
• Is the TH_M value above TH_M_MIN value?
Yes
Go to Step 8.
No
Replace the PCM, then go to Step 8.
(See PCM REMOVAL/INSTALLATION [L3 Turbo].)
7
VERIFY TROUBLESHOOTING OF DTC P0128:00 COMPLETED
• Start the engine and turn off E/L and A/C.
• Access the PIDs TH_M (Temp and Num units), TH_M_MAX (Num unit) and TH_M_MIN (Temp unit) using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [L3 Turbo].)
Note
• This test requires actual driving. Chassis roller cannot be used for this test.
• During 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 PIDs TH_M, TH_M_MAX and TH_M_MIN 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?
Yes
Go to the next step.
No
Replace the PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION [L3 Turbo].)
8
VERIFY AFTER REPAIR PROCEDURE
• Perform the “AFTER REPAIR PROCEDURE”. (See AFTER REPAIR PROCEDURE [L3 Turbo].)
• Are any DTCs present?
Yes
Go to the applicable DTC inspection.
(See DTC TABLE [L3 Turbo].)
No
DTC troubleshooting completed.