Introduction
The engine control system on the diavel uses a sensor that measures air temperature. This sensor has a resistance of ntc type (negative temperature coefficient), that reduces its own value when the temperature increases. The air temperature sensor allows the engine control unit to modify the fuel-air mixture and ignition advance in relation to the atmospheric air temperature.
Components assembling position

The air temperature sensor is mounted on the right hand air intake (the image also shows the location of the connection).
Wiring diagram

Ccm engine control connection, s air temperature sensor. 1 Green/blue - g/b, 2 black/purple - bk/v.
In the event of fault
In the event of an air temperature sensor fault, the engine control unit implements a recovery value of 25C.
Fault codes generated and possible correlated faults
Fault codes generated by the engine control unit and displayed by the dds (intake air temperature sensor diagnosis):
Note
Check integrity of electric circuit - short-circuit to vdc = with dashboard on, using a voltmeter, a voltage is measured between the wire tested and ground.
Check integrity of electric circuit - short-circuit to ground = with the battery cables disconnected, using an ohmmeter, continuity is detected between the wire tested and ground.
Check integrity of electric circuit - open circuit = with the battery cables disconnected, using an ohmmeter, no continuity is detected between the two ends of the wire tested.
The dashboard service display shows the error "air temperature" and the eobd warning light activates.
Possible correlated faults: inadequate engine power, irregular idle speed (target idle speed is 1350 rpm with engine stabilised at operating temperature), the engine does not start easily. Check: -sensor resistance, which must be approximately 2 kohm at 25 C.
The air temperature value may be checked using the dds. Check that the value given is plausible.
If none of the aforementioned tests identify the problem and the air temperature sensor is in proper working order, replace the engine control unit.
Component replacement methods
No special measures are necessary in order to replace the air temperature sensor.
Component assembling position
Engine temperature sensorOverhaul of the cylinder barrel/piston components
Overhauling the cylinder
Check that the walls of the cylinder bore are perfectly smooth. Measure the
cylinder bore diameter at 50 mm from the top
face and determine the size class to which it belongs in accordance with the
values specified in sect. 3 -
1.1Cylinder/piston. Repeat measurement o ...
Removal of the generator cover
Note
This operation is described for an engine removed from the frame since all
reassembly procedures are easier with the
engine on the bench.
Disconnect the connector (a) from the generator cable.
Unscrew the two retaining screws (7) of the centre cap (6) over the end of
the cranksh ...
Refitting the cylinder heads pulleys/fixed tensioners
Check that the keyway on the end of the camshaft is in good condition and
without burrs.
Fit a woodruff key (b) in the keyway of each camshaft.
Fit the pulley (11) on the camshaft, inserting the woodruff key in the in the
slot (c) in the pulley.
Apply the recommended grease to the t ...