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
• ◆ Test box V.A.G 1598/18
• ◆ Adapter set V.A.G 1594
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Diode test lamp V.A.G 1527
• ◆ Current flow diagram

Test conditions

• ● Fuses 18, 21 and 22 must be OK.
• ● Vehicles 08.95 ▸:Idling speed switch OK, checking ,
  checking throttle valve control part.
• ● Vehicles ▸07.95: Throttle valve potentiometer (G69) OK.

Notes:

• ◆ The final control diagnosis can only be carried out if the engine is stationary and ignition switched on.
• ◆ The final control diagnosis will be broken off if the engine is started or a rotational impulse is recognised.
• ◆ During the final control diagnosis the individual final controls will be activated until advancing to the next final control by pressing the ⇒ button.
• ◆ The final controls are checked acoustically or by touching.
• ◆ If it is necessary to repeat the final control diagnosis, without first running the engine briefly, switch the ignition off for approx. 5 seconds.
• ◆ The electric fuel pump will run during the complete final control diagnosis.
• ◆ The final control diagnosis will be aborted after 10 minutes.

Work sequence

The final control diagnosis activates the following components in the stated sequence:

     1)     Vehicles 08.95 ▸:Ignore display

     2)     Ignore display

Note:

Injector activation sequence:

• ◆ Vehicles with distributor: 1-5-3-6-2-4
• ◆ Vehicles with distributor less ignition: Cylinder 1...6

• ‒ Connect the fault reader V.A.G 1551 (V.A.G 1552). Then switch ignition on and select engine control unit with the "Address word" 01.
  (Connecting fault reader and selecting engine control unit .)

• ‒ Operate fault reader taking into account the information on the display:
• ‒ Press keys 0 and 3 for the function "Final control diagnosis".

Note:

If something different is indicated on the display:

=> Fault reader operating instructions

Activate injectors (N30...N84):

• ‒ Confirm input with Q key.

Note:

The fuel pump must run and the flow noise must be distinctly audible at the fuel pressure regulator. If the fuel pump does not run, check activation.

=> Repair group 20; Removing and installing parts of the fuel system; Checking fuel pump

• ‒ Open throttle valve fully and close again.
       The Cyl. 1 injector must click

To activate injectors, Cyls. 2...6 in each case:

• ‒ Press the ⇒key.
• ‒ Open throttle valve fully again and close.

Skipping individual tests:

• ‒ Press the ⇒key.

If one or more injectors do not click:

• ‒ Continue final control diagnosis to the end.
• ‒ Switch off ignition.
• ‒ Checking injector actuation (resistance and current supply) => Page 24-83 , checking injectors.

Activate idling stabilization valve (N71):

• ‒ Press the ⇒key.

• The idling stabilization valve must click, until switching to the next final control by pressing the ⇒button.

If the idling stabilization valve does not click:

• ‒ Switch off ignition.
• ‒ Pull connector off valve.
• ‒ Connect diode test lamp V.A.G 1527 with aux. cables from V.A.G 1594 to contacts 1 and 2 of detached connector.
• ‒ Switch on ignition.
• ‒ Repeat final control diagnosis -idling speed stabilization valve (N71)-.
       LED must flash

LED flashes:

• ‒ Renew idling stabilization valve.

LED does not flash:

• ‒ Proceed with final control diagnosis until completed.
• ‒ Switch off ignition.

• ‒ → Connect test box V.A.G 1598/18 to control unit wiring harness.
• ‒ Check wire between test box socket 27+2 pin connector contact 1 and test box socket 53+2 pin connector contact 2 for open circuit using current flow diagram.
       Wire resistance: max. 1.5 ω
• ‒ Additionally check wire for short to battery positive and earth.
       Specification: ∞ω

If no wiring fault is detected:

• ‒ Renew engine electronics control unit => Page 24-116 .

Activating activated charcoal filter solenoid valve 1 (N80):

• ‒ Press ⇒key.

• The activated charcoal filter solenoid valve 1 (on air cleaner housing) must click until the next final control is activated by pressing ⇒key.

The valve clicks but a fault is still suspected (valve does not open or close):

• ‒ Pull hose off activated charcoal filter at solenoid valve.
• ‒ Connect an auxiliary hose to the vacant valve connection.
• ‒ During final control diagnosis blow into auxiliary hose (in direction of throttle housing).
       Valve must open and close

If the solenoid valve does not click:

• ‒ Pull 2 pin connector off valve and connect diode test lamp V.A.G 1527 with aux. cables from V.A.G 1594 to disconnected connector.
       The LED must flash

LED flashes:

• ‒ Renew solenoid valve.

=> Repair group 20; Removing and installing parts of activated charcoal filter system

LED does not flash:

• ‒ Switch off ignition.
• ‒ Check wiring connections according to current flow diagram.

=> Current flow diagrams, Electrical fault finding and Fitting locations binder

If no wiring fault is detected:

• ‒ Renew Motronic control unit (J220) if necessary.

Activate Lambda probe heating relay (J278):

• ‒ Press ⇒key.

• The Lambda probe heating relay (on additional relay plate) must click until the next control element is activated by pressing the ⇒ button.

If the relay does not click:

• ‒ Switch off ignition.
• ‒ Check wiring connections according to current flow diagram.

If an open circuit cannot be located:

• ‒ Renew Lambda probe heating relay (J278) or Motronic control unit (J220) as necessary.
• ‒ Press ⇒key.

• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.

Note:

After completion of the final control diagnosis switch off ignition. If the ignition is not switched off before attempting to start, the engine will not run, as the injectors and the ignition transformer will not be activated.