P0128-ENGINE COOLANT TEMP SENSOR ENGINE IS COLD TOO LONG

For a complete wiring diagram Refer to Section 8W

When Monitored:
With the engine running and engine temperature is below 34 degrees C.
Set Condition:
Engine temperature does not increase enough during a calibrated amount of time.

Possible Causes

ENGINE COLD TOO LONG

Diagnostic Test

1. CHECK COOLING SYSTEM PERFORMANCE

NOTE: The best way to diagnose this DTC is to allow the vehicle to remain outside overnight in order to have a completely cold soaked engine.

NOTE: Extremely cold outside ambient temperatures may cause this DTC to set.

Verify that the coolant level is correct.
Start the engine.
With the scan tool, set the engine RPM to 1500 and allow the engine to warm up for 10-15 minutes.
With the scan tool, monitor the Engine Coolant Temperature value during the warm up cycle. Make sure the transition of temperature change is smooth.

Did the engine temperature reach a minimum of 80 degrees C (176 degrees F)?

Yes

Test Complete.

No

Refer to the Service Information for cooling system performance diagnosis. The most probable cause is a Thermostat problem. Also, refer to any related TSBs. If there are no cooling system problems replace the Engine Coolant Temperature Sensor.

Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)