2000 AUDI A8 AHA Engine Auxiliary Signals Checking Workshop Manual

Read safety precautions for test driving vehicles
while using test equipment page 24
-9 .

The speed signal is generated by the vehicle
speed sensor (at the transmission), and
processed at the speedometer/odometer in the
instrument cluster.
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Test procedure

- Connect VAG1551 or VAG1552 scan tool 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 Measurin
g Value Block
HELP
Input displa
y group number XXX

Indicated on display
- Press buttons -0-, -0- and -5- to input display group number 5 (005),
and press -Q- button to confirm input.
Read Measuring Value Block 5 1 2 3 4

Indicated on display (1-4 = display fields)
- Road test and compare indicated vehicle speed with value in display
field 3 (2nd technician required, Safety precautions page 24
-9 ).
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Display fields

1 2 3 4
Display group 5: General engine data
Display xxx RPM xx.xx ms xxx km/h Idle
Part throt
Full throt
Decel
Enrich
Indicates Engine speed
(in 40 RPM
steps) Engine load Vehicle speed Operating
condition
Range 0 - 6800 RPM 0.00 - 12.75
ms 0 - 326 km/h ---
Specified
value --- --- Approx. vehicle speed ---

--- --- If no vehicle speed is displayed page 24
-171
,
Continuation
---
If displayed value is OK:

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

- Switch off ignition.
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Continuation
If no speed was indicated:

Notes:
If the LED does not blink:
If the wiring is OK and the LED does not blink:
Repair Manual, Electrical Equipment, Repair Group 90
- Connect VAG1598/22 test box to ECM harness connector page 01
-
67
.
- Connect VAG1527B LED voltage tester between ECM/test box sockets
3 (B+) and 20 (signal).
- Lift vehicle at left-front until wheel is free.
- Switch ignition on and rotate left-front wheel by hand.
LED must blink (very brief blink)
The right-front wheel must not rotate; block it if necessary.For LEDs with little voltage consumption, the LED lights up at half
strength when the ignition is switched on.
- Check wiring from ECM connector, terminal 20 to instrument cluster for
open circuit or short circuit Electrical Wiring Diagrams,
Troubleshooting & Component Locations binder.
-
Check readiness code page 01
-70
. If Diagnostic Trouble Code
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(DTC) memory has been erased, or ECM was disconnected, generate
new readiness code page 01
-73
.
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CAN-Bus, checking

When a CAN-Bus malfunction is indicated during
a check of DTC memory of the Engine Control
Module (ECM), refer to the following test to
eliminate the malfunction.

Note:

The information exchange occurs between the
Engine Control Module (ECM) and the
Transmission Control Module (TCM) via a CAN-
Bus.
All signals are carried by 2 wires between the
ECM and the TCM.

Required special tools and test equipment
VAG1551 or VAG1552 Scan Tool (ST) with
VAG1551/3 adapter cable
VAG1598/22 test box
VW1594 connector test kit
Wiring diagrams
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Checking

- Check DTC memory of Transmission Control
Module (TCM).
Repair Manual, 5 Spd. Automatic
Transmission 01V, Repair Group 01 If a DTC regarding the CAN-Bus wire is also
stored in the TCM:

- Switch ignition off.

Electrical Wiring Diagrams, Troubleshooting & Component Locations
binder
If wiring is OK: - Connect VAG1598/22 test box to ECM harness connector page 01
-
67
.
- Check wires from terminal 29 and terminal 41 of test box to
transmission control module for open or short circuit per wiring
diagram. - Replace Transmission Control Module (TCM) and Engine Control
Module (ECM) as necessary and in sequence.
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