1995 AUDI A8 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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Read Measurin
g Value Block
HELP
Input display group number XXX

Indicated on display
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28-9

- Press buttons corresponding to following display
group numbers and press -Q- button to confirm
input.


022: Display group 22, for cylinders 1 and
2

023: Display group 23, for cylinders 3 and
4

024: Display group 24, for cylinders 5 and
6
Read Measuring Value Block 22 1 2 3 4

Indicated on display (1-4 display groups)
Note:
The test must be carried out during a road test because the knock sensor
system is only active with engine speed greater than 2600 RPM and
engine load greater than 3 ms.
WARNING!
A second technician is required to operate the VAG1551 scan tool
during the road test. Safety precautions page 24
-9 .
- Road test and compare display with specified values for knock sensor
system in display field 1-4.
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28-10


Display fields

1 2 3 4
Display group 22 1): Knock control
Display xxx RPM xx.xx ms
xx.x
xx.x
Display Engine speed
(in 40 RPM
steps) Engine load Ignition angle correction 1 Ignition angle correction 2
Work range 0 - 6800 RPM 0.00 - 12.75
ms 0.0 - 12.0
(crankshaft)
0.0 - 12.0
(crankshaft)
Specified
Value ... RPM (test
drive) ... ms (test
drive) 0.0 - 10.0
(crankshaft)
0.0 - 10.0
(crankshaft)

--- --- If displayed values are NOT OK page 28
-11
, Evaluating display
groups 22, 23, 24
1) Display also valid for display groups 23 (cyls. 3 and
4) and 24 (cyls. 5 and
6) .
If displayed values are OK:

-
Press button.

- Press buttons -0- and -6- to select "End Output"
function 06, and press -Q- button to confirm
input.
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- 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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28-11
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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28-12

Continuation

- Disconnect 3-pin connector from Knock Sensor
(KS) 1 -G61-.

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 68
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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28-13


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 68
Connector terminal 3 to ECM/test box socket 68
Specified value:
- Loosen knock sensor and tighten to 20 Nm (15 ft lb).
- Replace Knock Sensor (KS) 1 -G61-.
- 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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