1995 AUDI A8 technical data

28-12

Misfiring recognition, checking


Required special tools and test equipment

VAG 1551 or VAG 1552 Scan Tool (ST) with
VAG 1551/3 adapter cable

Checking

- Connect VAG 1551/1552 Scan Tool (ST) and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (engine running at
idle) Page 01
-7 .
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, 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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28-13

- 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 0.00-8.50 ms --- ---
Specified value 760-960 RPM 0.5-1.5 ms 20 activated

--- --- If displayed values are NOT OK Page 28
-14

If displayed values are OK:

- Check readiness code Page 01
-59
. If
Diagnostic Trouble Code (DTC) memory has
been erased, or ECM was disconnected,
generate new readiness code Page 01
-62
.

-
Press button to advance program
sequence.
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- Press buttons -0- and -6- to select "End Output"
function 06, and press -Q- button to confirm
input.
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28-14
If displayed values are NOT OK:

- Press -C- button.

- Press buttons -0-, -1- and -5- to input display
group number 15, 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
-16
, Evaluating display groups 15 and 16
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28-15
If displayed values are OK:

- Press -C- button.

- Press buttons -0-, -1- and -6- to input display
group number 16, 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 activated
deact
Indicates Misfire harmful to emissions, Cyl. 4 Misfire recognition status
Range 500 ---
Specified value 0-5 activated

If displayed values are NOT OK Page 28
-16
, Evaluating display groups 15 and 16
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28-16
Evaluating display groups 15 and 16 Display groups: 15 and
16


Display fields: 1-4
Possible cause
Corrective action
larger than 5

Ignition coil faulty
Spark plug connector faulty
Spark plug faulty- Check ignition coil Page 28
-17


Power output stage for ignition coil
faulty - Check power output stage for ignition coil Page
28
-21



Fuel injector faulty
Not enough fuel- Check fuel injectors Page 24
-87
- Check fuel in tank
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