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.
Replacing the tank flange and fuel sensor
Loosen the screws (19) securing the fuel tank flange (20).
Remove the flange (20) from the tank (20).
Recover the seal (21).
Undo and remove the two fixing screws (g) and move the protection (f).
Before reassembly, carefully remove any deposits or scale from all parts.
Note
The flang ...
External components
Oil breather valve
O-ring
Sealing washer
Gear position sensor
Cylinder barrel/head stud
Nipple
By-pass spring
Plug
Plug
Aluminium gasket
Nut
Lock washer
Timing gear pair
Key
Key
O-ring
Screw
Locating dowel
Starter idler gear
Washer
Gear shaft
O-ring
...
Refitting the rear sprocket
Check the cush drive bushes (6) condition and, if necessary, replace them by
removing them from the flange.
Refitting is the reverse of removal.
Apply recommended grease on the rear sprocket flange (5) external diameter.
Place the rear sprocket flange (5) on sprocket (17) by inserting it ...