1998 AUDI A8 AHA Engine Motronic Ignition System Workshop Manual

28-14

- Disconnect 3-pin connector from Knock Sensor
(KS) 2 -G66-.

If resistance is OK (no continuity): - Connect multimeter US1119 (Fluke 83 or equivalent) to measure
resistance between connector terminals, using adapters from VW1594
connector test kit.

Connector terminals 1 and 2
Connector terminals 1 and 3
Connector terminals 2 and 3
Specified value:
- Connect VAG1598/22 test box to Motronic ECM harness connector
page 01
-67
.

- Check wiring for open circuit between ECM/test box and 3-pin harness
connector, according to wiring diagram.

Connector terminal 1 to ECM/test box socket 60
Connector terminal 2 to ECM/test box socket 67
Connector terminal 3 to ECM/test box socket 67
Specified value: max. 1.5
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28-15


If the wiring is OK:
If the malfunction still exists (stored in DTC memory): - Check wiring for short circuits between terminals of 3-pin connector,
and between connector and ECM/test box.

Connector terminal 2 to ECM/test box socket 60
Connector terminal 3 to ECM/test box socket 60
Specified value:
- Loosen knock sensor and tighten to 20 Nm (15 ft lb).
- Replace Knock Sensor (KS) 2 -G66-.
- 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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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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28-17

- Compare displayed values with specified values
for misfire recognition (display fields 3-4):

Display groups

1 2 3 4
Display group 14: Misfire recognition
Display xxx RPM xx.xx ms xxx activated
deact
Indicates Engine speed
(in 40 RPM
steps) Engine load Misfire harmful to emissions (total) Misfire recognition status
Range 0 - 6800 RPM 0.00 - 12.75
ms --- ---
Specified
value 620 - 740 RPM
(all-wheel drive) 1.0 - 2.5 ms 30 activated
740 - 860 RPM
(front-wheel
drive)

--- --- If displayed values are NOT OK page 28
-18
, display groups 15,
16
If displayed values are OK:
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-
Press button.
- Press buttons -0- and -6- to select "End Output"
function 06, and press -Q- button to confirm
input.

- 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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28-18
If displayed values are NOT OK:

- Press -C- button.

- Press buttons -0-, -1- and -5- to input display
group number 15 (015), and press -Q- button to
confirm input. Read Measuring Value Block 15 1 2 3 4

Indicated on display (1-4 display groups) - Compare displayed values with specified values for misfire recognition
(display fields 1-4):

Display groups

1 2 3 4
Display group 15: Misfire recognition
Display xxx xxx xxx activated
deact
Indicates Misfire harmful to
emissions, Cyl. 1 Misfire harmful to
emissions, Cyl. 2 Misfire harmful to
emissions, Cyl. 3 Misfire recognition
status
Range 500 500 500 ---
Specified
value 0 - 5 0 - 5 0 - 5 activated

If displayed values are NOT OK page 28
-20
, Evaluation of display groups 15 and 16
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28-19
If displayed values are OK:

- Press -C- button.

- Press buttons -0-, -1- and -6- to input display
group number 16 (016), and press -Q- button to
confirm input. Read Measuring Value Block 16 1 2 3 4

Indicated on display (1-4 display groups) - Compare displayed values with specified values for misfire recognition
(display fields 1 and 4):

Display groups

1 2 3 4
Display group 16: Misfire recognition
Display xxx xxx xxx activated
deact
Indicates Misfire harmful to
emissions, Cyl. 4 Misfire harmful to
emissions, Cyl. 5 Misfire harmful to
emissions, Cyl. 6 Misfire recognition
status
Range 500 500 500 ---
Specified
value 0 - 5 0 - 5 0 - 5 activated

If displayed values are NOT OK page 28
-20
, Evaluation of display groups 15 and 16
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28-20
Evaluation of display groups 15 and 16 Display groups: 15
and 16


Display fields: 2 and
3
Possible malfunction cause
Corrective action
greater than 5

Ignition coil faulty
Spark plug connector faulty
Spark plug faulty
Power output stage for
ignition coil faulty - Check ignition coils -N-, -N128- and -N158- with power output
stage -N122 page 28
-21



Fuel injector faulty
Not enough fuel- Check fuel injectors page 24
-102
- Check fuel in tank
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