Checking ignition transformer: Audi (AUA, BAH)

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required

Test box V.A.G 1598/22
Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
Adapter set V.A.G 1594
Diode test lamp V.A.G 1527
Current flow diagram

Check conditions

The fuses must be OK.
The battery voltage must be at least 11.5 V.
If the vehicle is equipped with an air conditioning system, this must be switched off.
All electrical consumers, e.g. lights and rear window heating must be switched off.
Hall sender must be OK, checking
=>Page
28-9
.
Engine speed sender must be OK, checking Page
24-63
.

Test sequence

Pull 4 pin connector off ignition transformer -arrow-.

Checking voltage supply

Using multimeter and adapter cables from V.A.G 1594 measure the supply voltage between contacts 2+4 of disconnected connector.
Switch on ignition.
Specification: min. 11.5 V
Switch off ignition.

If no voltage is present:

Check wire between 4 pin connector contact 2 and relay plate for open circuit according to current flow diagram.
Wire resistance: max. 1.5 ω
Check wire between 4 pin connector contact 4 and earth for open circuit according to current flow diagram.
Wire resistance: max. 1.5 ω

Checking activation

Warning!
During the following test do not touch the terminals of the ignition transformer or test cables.
Remove fuse 32 from fuse holder.

Note:

Removal of fuse 32 interrupts the voltage supply to the injectors.

Connect diode test lamp V.A.G 1527 with adapter cables from V.A.G 1594 to
contacts 1 + 4 (ignition output 1),
contacts 3 + 4 (ignition output 2)
of disconnected connector.

Operate starter and check the ignition signal from engine control unit.
The LED must flicker
Switch off ignition.

If the LED flickers and there is voltage between contacts 2 + 4:

Renew ignition transformer (N152)
=> Page
28-3
, item
2
.

The LED does not flicker:

Check wiring => Page
28-17

Checking wiring

Connect test box V.A.G 1598/22 to control unit wiring harness
=> Page
24-121
.

Check wires between test box and 4-pin connector (connector to control unit) for open circuit using current flow diagram..
Contact 1+socket 57
Contact 3+socket 71
Wire resistance: max. 1.5 ω
Additionally check wires for short to one another, to vehicle earth and to battery positive.
Specification: ∞ω

If no wiring fault is detected and voltage was present between contacts 2+4:

Replace engine control unit
=> Page
24-134
.

Checking secondary resistance

Check the secondary winding on terminal 4 between
Cyl. 1+Cyl. 4,
Cyl. 2+Cyl. 3.
Specification: 4.0... 6.0 kω (at 20 °C)

If the specifications are not attained:

Renew ignition transformer (N152)
=> Page
28-3
, item
2
.