4C89

4C89 - P0128

Information saved in
DDE

Fault code
4C89 - P0128

Fault text
DDE: Coolant temperature sensor, plausibility: Measured
temperature too low compared with modelled temperature

Fault description
The diagnostic trouble code is logged when the modeled
coolant temperature rises above the threshold 70 �C and the
measured coolant temperature is simultaneously below the
limit 60 �C.

Condition for fault identification
Test condition:
The following conditions must be met for the error check:
1. Engine rpm greater than 450 1/min.
2. Vehicle speed greater than 0 km/h.
3. For a period of 2700 s the temperature at engine start
must lie between -40 �C and 70 �C.
4. No other diagnostic trouble codes for the coolant-
temperature sensor should be present.
5. The outside temperature must be below -7 �C.
The test routine is executed continuously in a 1000 ms grid.
Voltage condition:
The following conditions must be met for the error check:
1. Engine rpm greater than 450 1/min.
2. Vehicle speed greater than 0 km/h.
3. For a period of 2700 s the temperature at engine start
must lie between -40 �C and 70 �C.
4. No other diagnostic trouble codes for the coolant-
temperature sensor should be present.
5. The outside temperature must be below -7 �C.
The test routine is executed continuously in a 1000 ms grid.

Condition for fault memory entry
Debounce (100 ms)

Action in service
-

Fault effect and breakdown warning
-

Driver information
Warning light:
MIL

Service instruction
none