Checking wiring between "white"/"brown" diagnostic connector and engine control unit — AUDI

Note:

This check must be performed if one of the following displays appears on the connected fault reader V.A.G 1551.

Rapid data transfer
Fault in communication link
Indicated on display:

or

Rapid data transfer
HELP
K-wire not switched to earth

or

Rapid data transfer
HELP
K-wire not switched to positive

or

Rapid data transfer
HELP
L-wire not switched to earth

or

Rapid data transfer
HELP
L-wire not switched to positive

Checking K and L-wires

Installation position of diagnostic connectors and wiring junctions K and L: In relay plate with fuse box in plenum chamber

Brown diagnostic connector - vehicles ä 07.91:

Note:

Vehicles ▸ 07.91 feature a direct wiring connection between engine control unit and brown diagnostic connector. In contrast, other vehicle systems with self-diagnosis are connected to the wiring junctions K and L.

With ignition switched off, use adapter V.A.G 1598/3 to connect test box V.A.G 1598A to engine control-unit connector only (not to control unit) => Page
24-20
.
Check for open circuit and short to earth/positive in the following wiring.

Brown diagnostic connector / Contact · Test box V.A.G 1598 A / Socket
1 · 23
2 · 22

If necessary, eliminate open circuit in wiring/short circuit.

=> "Current Flow Diagrams, Electrical Fault-finding and Fitting Locations" binder

White diagnostic connector - vehicles 08.91 ä:

Notes:

All the diagnostic wires of the various systems merge in the wiring junctions K and L. A defective wire (short to earth or positive)/a defective control unit may also result in one of the fault messages listed.
Determine wiring colour if wires with different cable colours are connected to wiring junction K or L.

=> "Current Flow Diagrams, Electrical Fault-finding and Fitting Locations" binder

If wires of the same colour are connected to wiring junction K or L, use test box V.A.G 1598 A (resistance measurement) to establish wire.

In this case proceed as follows for fault-finding purposes:

Consecutively disconnect wires of other vehicle systems with self-diagnosis from wiring junction K.

After unplugging connector to one vehicle system in each case, switch on ignition and then enter address word "01" for engine electronics again.

If engine control unit identification is then displayed:

After switching on ignition, enter address word "00" for automatic test sequence to establish the control unit to which the disconnected wire determined belongs.
Check diagnostic wire of disconnected control unit/replace control unit.
Start engine, let it idle and enter address word 01 for "Engine electronics" again => Page
01-2
.

If control unit identification is still not displayed:

With ignition switched off, use adapter V.A.G 1598/3 to connect test box V.A.G 1598A to engine control-unit connector only (not to control unit) => Page
24-20
.

Check for open circuit and short to earth/positive in the following wiring.

White / diagnostic / connector / Contact · Wiring / junction · Test box V.A.G 1598 A / Socket
1 · L · 23
2 · K · 22

If necessary, eliminate open circuit in wiring/short circuit.

=> "Current Flow Diagrams, Electrical Fault-finding and Fitting Locations" binder

Note:

Proceed in the same manner to check L-wire.