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Testing idling speed switch (vehicles without cruise control) > < Function

A3 Mk1

Motronic Injection and Ignition System (4-cyl.) 08.97ä
Testing throttle valve control part (vehicles without cruise control)
Performing adaption of throttle valve control part (vehicles without cruise control)

The adaption process enables the engine control unit to learn the stop positions from the throttle valve control part with the ignition switched off and the engine not running.

If the throttle valve control part -J338 is removed and refitted or replaced, or if the power supply of the engine control unit is interrupted, the adaption process must be performed.

Test conditions

  • ● No faults stored in fault memory
    =>Interrogating fault memory, Page 01-7
  • ‒ Connect fault reader V.A.G 1551 (V.A.G 1552) and select engine electronics control unit with the "Address word" 01. When doing this the ignition must be switched on.
    (Connecting fault reader and selecting engine electronics control unit .)

Note:

The adaption process for the throttle valve control part will be aborted in the following cases:

  • ◆ If the engine is started or if the accelerator is depressed while the adaption process is running.
 
→ Indicated on display:
Rapid data transfer    HELP
Select function XX
  • ‒ Press keys 0 and 4 for the function "Introduction of basic setting" and confirm entry with Q key.
 
→ Indicated on display:
Basic setting    HELP
Input display group number XXX
  • ‒ Press keys 0, 9 and 8 for Display Group 098 and confirm entry with Q key.
 
→ Indicated on display:
System in basic setting    98    ⇒
    x.xxx V    x.xxx V    Idling    ADP.runs

When the Q key is pressed the throttle valve positioner moves to the "Min." position and several intermediate positions, and the control unit records the various throttle valve angles in its non-volatile memory. The throttle valve then remains in the start position for a brief period before closing.
 
→ Indicated on display:
System in basic setting    98    ⇒
    x.xxx V    x.xxx V    Idling    ADP. O.K.
  • ‒ Press the⇒key to terminate the adaption process.
  • ‒ Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.

Note:
 
→ If one of the following messages appears on the display, this means that the adaption process has been aborted.
Basic setting 98    ⇒
    x.xxx V    x.xxx V    Idling    ADP.n.OK
 
Basic setting 98    ⇒
    x.xxx V    x.xxx V    Idling    ERROR
 
Function is unknown or
cannot be carried out at the moment

If the adaption process is aborted by the control unit, the cause could be one of the following:

  • ◆ The throttle valve cannot reach the mechanical idling stop because of a build-up of dirt (e.g. oil carbon deposits) or an incorrectly adjusted accelerator cable.
  • ◆ Battery voltage too low.
  • ◆ Throttle valve control part or wiring is defective.
  • ◆ The engine was started or the accelerator was depressed while the adaption process was running.

After an interruption the fault "Basic setting not completed, fault in basic setting" is stored in fault memory. When next switching on ignition the basic setting is automatically performed again.

Fault-finding:

  • ‒ If the adaption process was aborted, proceed as follows:
  • ‒ Press the ⇒key.
  • ‒ Interrogate fault memory.
 
→ If no faults are detected, check whether the idling speed switch opens and closes when the accelerator is depressed.
(Testing idling speed switch.)
No faults recognised    ⇒
 
→ If one of the following faults is detected, check whether the idling speed switch opens and closes when the accelerator is depressed. (Testing idling speed switch.)
Idling switch does not open    ⇒
Short circuit to earth
 
Idling switch does not close    ⇒
Open circuit
 
→ If this fault is displayed, test the voltage supply to the engine control unit (voltage at terminal 30 on engine control unit has dropped below 10 V). Testing voltage supply to engine control unit.
Voltage supply    ⇒
Signal too small
 
→ If one of the following faults is displayed, test throttle valve positioner sender -G127 and throttle valve potentiometer -G69.
Throttle valve positioner sender -G127    ⇒
Signal too small / too great
 
Throttle valve potentiometer -G69    ⇒
Signal too small / too great
 
Throttle valve positioner sender -G127    ⇒
Implausible signal
  • ‒ Repair faults, then repeat adaption of throttle valve control part.

Testing idling speed switch (vehicles without cruise control) > < Function