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 sensorRectifier-regulator
The rectifier (1) is placed in the electrical components compartment.
The rectifier/regulator consists of an aluminium casing containing the diodes
that rectify the current produced by the
alternator. It also contains an electronic device that regulates the current
supplied by the alternator ...
Disassembly of the oil pump
Hold the oil pump (1) in a vice taking care not to damage the drive gear
(12).
Warning
Make sure that vice jaws are faced with soft material.
Remove the plug (14) and extract the spring (16) and by-pass valve (17).
Check the condition of the above components.
Remove the circlip (6) ...
Dds diagnosis instrument
The main functions of the dds diagnosis instrument can be summarised as
follows:
Retrieval of errors (faults) of the ignition-injection system stored in
the engine control unit memory and their subsequent
deletion, if required.
Reading of engine parameters (rpm, coolant and air temperat ...