1997 AUDI A8 AHA Engine Motronic Ignition System Workshop Manual

28-21

Ignition coils and power output stage,
checking


Notes:

The ignition coils and power output stage are
one component.
Measuring the primary resistance of the ignition
coils is not possible.
Measure secondary resistance first with ignition
wires connected to the ignition coil via the spark
plug connector of the respective cylinder (with
this method the interference resistances of the
ignition cables are also measured).
Component locations page 24
-1

Required special tools and test equipment

Multimeter US1119 (Fluke 83 or equivalent)
VW1594 connector test kit

Test conditions
No fuel injector malfunction stored in DTC
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memory
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28-22

Checking

- Check DTC memory page 01
-16
.

There must be no malfunctions stored

- If DTC memory is not clear (malfunctions
recognized):

- Make necessary repairs and erase DTC
memory.

- Stop engine and start engine again.

- Road test.

- Check and erase DTC memory again.

- By briefly disconnecting fuel injector connectors
with engine running, check which cylinder is
misfiring, or not firing at all.
A misfiring cylinder can also be isolated by
examining the spark plugs (for a carbon-fouled
plug).

-
Interchange spark plug with one from cylinder
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that is OK.
If a different cylinder now misfires:

- Replace faulty spark plug.
If the original cylinder misfires:

- Check ignition coil page 28
-23
.
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28-23

Checking ignition coils -N-, -N128- and -N158-


- Disconnect 5-pin connector from ignition coil
assembly.

- Remove ignition wires from spark plugs.

If resistance is NOT OK: - Using multimeter and adapters from VAG1594 connector test kit,
measure resistance between both spark plug connectors of respective
ignition circuit (across coil).

Specification: approx. 18-25 k .- Remove ignition wires from ignition coils and measure resistance
between ends of respective ignition wires.

Specification: approx. 4.0-6.0 k
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28-24


If resistance values are not as specified:
If resistance values are OK: - Using multimeter and adapters from VAG1594 connector test kit,
measure resistance across both ignition wire connectors of respective
ignition coil.

Specification: 8.0-14.0 k - Replace coils.
- Check signal for power output stage page 28
-25
.
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28-25

Checking signal for power output stage

- Remove connectors from all 6 injectors (DTC
memory will have to be checked and erased
later).

- Switch ignition on.

If LED flashes: - Connect LED tester VAG1527 between engine ground and connector
terminal 3.
- Crank starter for several seconds.
LED in voltage tester must flash.
- Repeat test on 5-pin connector terminals 4 and 5.
- Replace ignition coils -N-, -N128- and -N158- with power output stage -
N122-.
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28-26
If LED does not flash:

- Connect VAG1598/22 test box to ECM harness
connector page 01
-67
.

If wiring is OK: - Check wiring between ECM/test box and 5-pin connector for continuity
and/or short circuit per wiring diagram.

Connector terminal 3 to ECM/test box socket 71
Connector terminal 4 to ECM/test box socket 78
Connector terminal 5 to ECM/test box socket 70
- Replace Motronic ECM -J220- page 01
-68
.
- Carry out adaptation of throttle valve control module to ECM page
24
-150
.
- Check readiness code page 01
-70
.
If Diagnostic Trouble Code (DTC) memory has been erased, or ECM
has been disconnected, generate new readiness code page 01
-73
.
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