DTC P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) [04/2013 - 06/2014]: Procedure
WARNING: This page is about a different car, the 2015 Lexus IS 250 and 2014 Lexus IS 250. However, it is still accessible from the selected car via links, so may be relevant.
- CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0128)
- Connect the Techstream to the DLC3.
- Turn the engine switch on (IG).
- Turn the Techstream on.
- Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
- Read the DTCs.
Powertrain > Engine > Trouble Codes
Result
Result Proceed to DTC P0128 is output A DTC P0128 and other DTCs are output B HINT:
If any DTCs other than P0128 are output, troubleshoot those DTCs first.
Result:
B
GO TO DTC CHART. Refer to DIAGNOSTIC TROUBLE CODE CHART [04/2013 - 06/2014]
Result:
A
See step 2
- CHECK COOLING SYSTEM
- Check for defects in the cooling system that might cause the system to be too cold, such as abnormal cooling fan operation or any modifications.
Result
Proceed to OK NG
Result:
NG
REPAIR OR REPLACE COOLING SYSTEM
Result:
OK
See step 3
- Check for defects in the cooling system that might cause the system to be too cold, such as abnormal cooling fan operation or any modifications.
- INSPECT WATER INLET WITH THERMOSTAT SUB-ASSEMBLY
- Inspect the water inlet with thermostat sub-assembly (thermostat opening temperature).
Refer to INSPECTION [04/2013 - 08/2015]
Result
Proceed to OK NG
Result:
OK
REPLACE ECM. Refer to REMOVAL [04/2013 - 08/2015]
Result:
NG
REPLACE WATER INLET WITH THERMOSTAT SUB-ASSEMBLY. Refer to REMOVAL [04/2013 - 08/2015]
- Inspect the water inlet with thermostat sub-assembly (thermostat opening temperature).