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Replacing, coding and matching engine control unit > < Checking engine operating mode

Golf Mk4

Motronic injection and ignition system (5-cyl. engine)
Checking functions
Checking driving characteristics after a cold start

If faults appear after a cold start check if problem occurs before or after the Lambda regulation is effected.

The Lambda regulation is introduced when the relevant probe temperature is approx. 300 °C.

The time taken to reach this temperature is dependent upon the following factors:

  • ◆ Ambient temperature (summer/winter)
  • ◆ Operating conditions after starting
  • ◆ Probe heater function

Test conditions

  • ● No faults regarding Lambda regulation are stored
    , interrogating fault memory

Test sequence

Check vehicle under cold start conditions during a test drive.

Note:

A 2nd person is required when performing a test drive.

Warning!
Secure fault reader to rear seat and operate from this position.
  • ‒ Connect fault reader V.A.G 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control unit. When doing this the engine must be running at idling speed.
    (Connecting fault reader and selecting engine control unit => Page 01-4 .)
 
→ Indicated on display:
Rapid data transfer     HELP
Select function XX
  • ‒ Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.
 
→ Indicated on display:
Read measured value block     HELP
Input display group number XXX
  • ‒ Press keys 0, 3 and 3 for "Display group number 33" and confirm entry with Q key.
 
→ Indicated on display:
(1...4 = Display zones)
Read measured value block 33     ⇒
     1     2     3     4
  • ‒ Carry out a test drive, when doing this observe probe voltage in display zone 2.
    • The voltage for a cold vehicle when the Lambda regulation is not working must be
           0.45...0.50 V.
     
    → When Lambda regulation is activated, the voltage signal in display zone 2 must fluctuate between 0.0...1.1 V.
    Read measured value block 33     ⇒
         1     2     3     4

    Note:

    Voltage values above 0.7 V indicate a rich mixture.

    Voltage values below 0.3 V indicate a lean mixture.

    If poor engine running characteristics are observed before the Lambda regulation commences:

    The fault does not lie within the Lambda regulation.

    Notes:

    • ◆ If the fault gets somewhat better after the regulation commences the cause of the fault (e.g. unmetered air, defective injectors, etc.) is somewhat neutralised by the regulation measures. This can be recognised when reading the Lambda learnt values.
    • ◆ With the aid of display group 99 the Lambda regulation can be switched on and off at will. Pressing buttons 4 or 8 switches back and forth between "Basic setting" (Lambda regulation off) and "Read measured value block" (Lambda regulation on).

    If poor engine running characteristics occur after the Lambda control commences:

    • ‒ Check Lambda regulation .

    Replacing, coding and matching engine control unit > < Checking engine operating mode