Test results

Check that the water temperature sensor is working properly by carrying out the

 See Test 1056BC Engine coolant temperature sensor operation check

Go to Step 4

Sensor defective

Replace the sensor

 Op. 1056B50 ENGINE COOLANT TEMPERATURE SENSOR - R + R

Sensor wiring connection irregular

Restore the correct connection

Connect the Examiner diagnostic equipment to the engine control unit.

Check:

- that there are no errors in the control unit;

- parameter plausibility.

Go to Step 2

Error detected in the control unit

Continue following the instructions on the diagnostic equipment

Parameters not plausible

Continue following the instructions on the diagnostic equipment

Connect the Examiner diagnostic equipment to the climate control system control unit.

Check:

- that there are no errors in the control unit;

- parameter plausibility.

Go to Step 3

Onset of error in control unit detected

Continue following the instructions on the diagnostic equipment

Parameters not plausible

Continue following the instructions on the diagnostic equipment

Check the continuity of the connections between the engine management control unit and fuse control unit

Check that the fan control relays are working properly

 See E5020 ENGINE COOLING

Go to Step 5

Wiring defective

Restore the correct wiring.

Relays defective

Replace the relays

Check that the thermostat is working properly

Go to Step 6

Thermostat defective

Replace the thermostat

 Op. 1088C40 THERMOSTAT- R + R

Check that the engine control unit is working properly

End of diagnosis

Engine management control unit defective

Replace the engine management control unit

 Op. 1056B82 INJECTION/IGNITION SYSTEM E.C.U. (ONE) - R + R