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.
Water pump
Screw
Washer
Circlip
Water pump outlet union
Bearing
bearing
Spacer
Aluminium gasket
Mechanical seal
Water pump impeller
Bush
Water pump cover assembly
Screw
Plug
Sealing washer
Generator cover
Special washer
Fuel filler flange
Spare parts catalogue
Diave ...
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 ...
Refitting the steering head components
Important
The steering tube bearings (6) are identical but in no case may their
components be swapped around during reassembly.
Clean all contact surfaces and lubricate with the recommended grease.
To fit the external rings (c) of the bearings (6) to the steering tube, use the
tool with par ...