check engine AUDI A8 1998 D2 / 1.G AHA Engine Motronic Ignition System Workshop Manual

28-8

Knock sensor and knock sensor control,
checking


Required special tools and test equipment

VAG1551/1552 Scan Tool (ST) with
VAG1551/3 adapter cable
VAG1598/22 test box
Multimeter US1119 (Fluke 83 or equivalent)
VW1594 connector test kit
Wiring diagrams

Checking

- Connect VAG1551/1552 Scan Tool (ST) and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with engine
running at idle) page 01
-8 .
Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block"
function 08, and press -Q- button to confirm input.
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28-11
Evaluation of display groups 22, 23 and 24 Display groups: 22, 23 and 24
Possible malfunction
cause
Corrective action
Display fields: 3, 4


All cylinders retarded more than
10 (crankshaft)
Knock sensor faulty- Continuation page 28
-12

Connector corroded
Knock sensor
incorrectly torqued - Loosen knock sensor and tighten to 20 Nm (15 ft lb)
Components loose on
engine - Tighten components
Poor fuel quality- Change fuel
Value for one cylinder different
from the others Connector corroded- Continuation page 28
-12

Engine damage- Check compression Repair Manual, 2.8 Liter V6 5V
Engine Mechanical, Repair Group 15

Components loose on
engine - Tighten components
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28-16

Misfire recognition, checking


Required special tools and test equipment

VAG1551 or VAG1552 Scan Tool (ST) with
VAG1551/3 adapter cable

Checking

- Connect VAG1551/1552 Scan Tool (ST) and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with engine
running at idle) page 01
-8 .
Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block"
function 08, and press -Q- button to confirm input.
Read Measuring Value Block
HELP
Input displa
y group number XXX

Indicated on display
- Press buttons -0-, -1- and -4- to input display group number 14 (014),
and press -Q- button to confirm input.
Read Measuring Value Block 14 1 2 3 4

Indicated on display (1-4 display groups)
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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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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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28-28

Checking voltage supply of ignition coils

Test requirement

Fuse for ignition coils OK

- Disconnect 5-pin connector from ignition coils.

- Switch ignition on.

If LED does not light up:
Electrical Wiring Diagrams, Troubleshooting & Component Locations
binder - Connect VAG1527 LED voltage tester between engine ground and
terminal 1 (B+) of connector.
LED in tester must light up.
- Check wires for open circuit per wiring diagram.
- Check fuse for ignition coils.
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