939003581 - D072 CRUISE CONTROL SET+ CONTROL NOT WORKING

The Cruise Control system does not increase the speed when the ring nut is turned to "SET+".
For safety reasons the Cruise Control is inhibited above a maximum speed and below a minimum speed. If these speeds are exceeded the Cruise Control no longer works
0PRELIMINARY CHECKALL OKPROBLEMS ENCOUNTEREDACTION
Check, by carrying out a road test, then the vehicle speed is higher than 40 km/h when the SET+ ring nut is adjustedMove on to Step 1Speed below 40 Km/hBring the speed to above 40 Km/h
1CHECK USING DIAGNOSTIC EQUIPMENTALL OKPROBLEMS ENCOUNTEREDACTION
Connect the diagnostic test equipment (Examiner or other instruments) to the tester input.Check for the presence of faults in the engine management control unitMove on to Step 21. Error detected in the control unit1. Continue following the instructions for the diagnostic equipment
2. No communication with the control unit2. Restore the connection between the engine management control unit and the diagnostic connector:    See E5060 CRUISE CONTROL
2CHECK USING DIAGNOSTIC EQUIPMENTALL OKPROBLEMS ENCOUNTEREDACTION
Connect the diagnostic equipment to the engine management control unit and check that the SET+ position for the lever with the correct operaiton of the Cruise Control system contactsCheck the continuity of the Cruise lever contacts    See Test 5580AB Cruise Control SET + control checkMove on to Step 31.No continuity for lever contacts1.Replace the Cruise Control lever assembly    Op. 5580A10 CRUISE CONTROL LEVER ASSEMBLY - R+R
2.Power supply to lever interrupted2.Move on to Step 3
3SUPPLY CHECKALL OKPROBLEMS ENCOUNTEREDACTION
With the ignition key in the ON position and the Cruise Control in the ON position and the ring nut at "Set+", check that there is a voltage signal from the Cruise Control to the engine management control unit:    See E5060 CRUISE CONTROLMove on to Step 4No voltage detected due to broken wiringRepair the connections:    See E5060 CRUISE CONTROL
4CHECK ON CORRECT OPERATIONALL OKPROBLEMS ENCOUNTEREDACTION
Check that the fault is no longer present by carrying out    See Test 5580AE CRUISE CONTROL OPERATION ROAD TESTEnd of diagnosisThe fault persists: engine management control unit defectiveReplace the engine management control unit    Op. 1056B82 INJECTION/IGNITION SYSTEM E.C.U. (ONE) - R + R