Volkswagen Workshop Service and Repair Manuals

Special tools, testers, measuring instruments and auxiliary items required

• ◆ Fault reader V.A.G 1551 or vehicle system tester V.A.G 1552 with
       ▸ 07.93: Cable V.A.G 1551/1
       08.93 ▸: Cable V.A.G 1551/3

Note:

The vehicle system tester V.A.G 1552 can be used instead of the fault reader V.A.G 1551, however a print-out is not possible.

Test conditions

• ● Fuses 21 or 22 must be OK.
• ● The battery voltage must be at least 11.5 V.
• ● Earth connections on engine and gearbox OK.
  (Earth connection engine: On the intake manifold upper part support or on intake manifold lower part.

Work sequence

Vehicles 08.93 ▸

• ‒ → Open ashtray, remove if necessary and slide cover for diagnostic connections to left -arrow-.
• ‒ Connect fault reader with cable V.A.G 1551/3.

Vehicles ▸07.93

• ‒ → Unclip covers for diagnostic connections below the heating/ventilation controls.
• ‒ Connect fault reader V.A.G 1551 with cable V.A.G 1551/1 as follows:
• ‒ First connect black plug for the fault reader voltage supply to black diagnostic socket.

* Appears alternately

Note:

If the display remains blank:

=> Fault reader operating instructions

• ‒ Connect white plug to white diagnostic socket. (The blue plug is not required.)
• ‒ Connect fault reader V.A.G 1551 with cable V.A.G 1551/3.

After the fault reader has been connected:

• ‒ Depending upon desired function:
  Switch ignition on
       or
  Start engine , Table "Selectable functions".

Notes:

• ◆ If the display remains blank, check voltage supply for diagnostic connection => Fault finding programme in "Current flow diagrams, Electrical fault finding and Fitting locations" binder
• ◆ If the display does not indicate as described in the work sequence:

=> Fault reader operating instructions

• ◆ If due to an input fault "Fault in the data transfer!" is displayed, pull wire off fault reader, reconnect and repeat work step.

• ‒ Operate fault reader taking into account the information on the display:
• ‒ Press key 1 for "Rapid data transfer".
• ‒ Press keys 0 and 1 for address word "Engine electronics" and confirm entry with Q key.

Control unit identification

for vehicles 08.95 ▸

• ◆ 021 906 256 = Part No. of the control unit (for latest control unit version see parts catalogue)
• ◆ MOTRONIC M3.8.1 = Injection and ignition system
• ◆ HS V02 = Manual gearbox with Motronic system version 02 (control unit must be coded after being renewed ).
• ◆ AT V02 = Automatic gearbox with Motronic system version 02 (conrol unit must be coded after being renewed ).
• ◆ Coding xxxxx = Control unit coding, coding table => Page 24-118
• ◆ WSC xxxxx = Workshop code from V.A.G 1551, of the workshops who carried out the last coding. (If the factory coding has not been changed, WSC 00000 appears)

Notes:

Replace control unit if the control version displayed does not correspond to the vehicle

=> Page 24-116 .

An incorrectly coded engine control unit leads to:

• ◆ Engine running faults (gearchange jerks, load change jerks, etc.)
• ◆ Increased fuel consumption
• ◆ Increased exhaust gas emissions
• ◆ Faults stored in fault memory which are not actually present
• ◆ Functions will not be performed (Lambda regulation, activation of the activated charcoal filter system, etc.).
• ◆ Reduced gearbox life

If the coding differs from the vehicle version, then:

• ‒ Checking control unit coding => Page 24-118 ,
  coding engine control unit
• ‒ Press ⇒key.

Control unit identification

for vehicles 08.93 ▸

• ◆ 021906256Q = Part No. of the control unit (for latest control unit version see parts catalogue)
• ◆ Coding HS = Coding variants (HS for manual gearbox)

Notes:

• ◆ Only with the engine running at idling speed will the correct control unit number and coding be displayed.
  Coding:
  HS = Manual gearbox
  AT = Automatic gearbox
• ◆ If the Motronic control unit is replaced in a vehicle with an automatic gearbox, initially the "Coding HS" for manual gearbox will appear in display. After starting the engine and moving the selector lever to selector lever position "D" the Motronic control unit will recognise the automatic gearbox. The display will then show the "Coding AT".

The code unit shown on the display will not be used by the Motronic control unit until the ignition has been switched off once.

An incorrect coding leads to:

• ◆ Engine running faults
• ◆ Increased fuel consumption
• ◆ Increased emissions
• ◆ Faults stored in fault memory which are not actually present
• ◆ Reduced gearbox life

Control unit identification

for vehicles ▸ 07.93

• ◆ 021906258AF = Part No. of the control unit (for latest control unit version see parts catalogue)
• ◆ Coding 1 = Coding variants

Notes:

Only with the engine running at idling speed will the correct control unit number and coding be displayed.

Coding:

1 = Manual gearbox and engine without exhaust gas recirculation system

2 = Automatic gearbox and engine without exhaust gas recirculation system

Replace control unit if the control version displayed does not correspond to the vehicle

=> Page 24-116 .

An incorrectly coded engine control unit leads to:

• ◆ Engine running faults (gearchange jerks, load change jerks, etc.)
• ◆ Increased fuel consumption
• ◆ Increased exhaust gas emissions
• ◆ Faults stored in fault memory which are not actually present
• ◆ Functions will not be performed (Lambda regulation, activation of the activated charcoal filter system, etc.).
• ◆ Reduced gearbox life

If the coding differs from the vehicle version, then:

• ‒ Checking control unit coding => Page 24-118 ,
  coding engine control unit
• ‒ Press the ⇒key.

• ‒ Further measures see repair procedures.