P0128

Test 1:

Test 2 - Test 4:

Test 5 - Test 7:

Test 8 - Test 12:

Test 13:

SYMPTOM
P0128-THERMOSTAT RATIONALITY

WHEN MONITORED
Engine running.

SET CONDITION
The PCM predicts a coolant temperature value that it will compare to the actual coolant temperature. A significant difference results in an error. Two Trip Fault.

POSSIBLE CAUSES
- Good trip equal to zero
- Other possible causes
- Low coolant level
- Thermostat operation
- Signal circuit shorted to battery voltage
- Temperature sensor
- Signal circuit open
- (K900) Sensor ground circuit open
- Signal circuit shorted to ground
- Signal circuit shorted to (K900) sensor ground
- PCM