1998 AUDI A8 ignition

24-129

Function

Idle speed stabilization is integrated in the
throttle valve control module -J338-. In the
housing opposite the throttle valve are Throttle
Position (TP) sensor -G69-, Closed Throttle
Position (CTP) switch -F60-, throttle drive -G186-
and angle sensor -1- for throttle drive -G187-.

The housing should not be opened.
The individual components cannot be replaced or
mechanically adjusted. All adjustments are
accomplished by the VAG1551 Scan Tool (ST)
using the "Basic Setting" function 04.
If the complete throttle valve control module is
without power (i.e. disconnected), the throttle
valve assumes a mechanical closed throttle
position that results in an increased idle speed of
1200-1300 RPM (with engine at operating
temperature).
If only the Throttle Position (TP) actuator -V60- is
without power, the throttle valve also assumes a
mechanical closed throttle position (limp-home
position), but because the signal from the CTP
switch -F60- can still be recognized, a nearly
"normal" idle speed of approx. 900 RPM is
maintained with a corresponding reduction of the
ignition timing advance.
If the Engine Control Module (ECM) recognizes a
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24-130

Throttle valve control module power
supply, checking


If voltage is NOT OK: - Disconnect 8-pin harness connector from throttle valve control module
-J338-.
- Connect multimeter US1119 (Fluke 83 or equivalent) between harness
connector terminals using adapter cables from VW1594 connector test
kit.
- Switch ignition on, and check voltage. Specified values:

Connector terminals 3 and 7 (Ground): 9.0-14.5 volts
Connector terminals 4 and 7 (Ground): 4.0-6.0 volts
- Switch ignition off.
- Connect VAG1598/22 test box page 01
-67
.
- Check wiring for open circuit between ECM/test box and 8-pin harness
connector.

Connector terminal 3 to ECM/test box socket 69
Connector terminal 4 to ECM/test box socket 62
Connector terminal 7 to ECM/test box socket 67
Specified value: max. 1.5
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24-134

Continuation

- Switch ignition off.

- Connect VAG1598/22 test box to ECM harness
connector page 01
-67
.

- Connect multimeter US1119 (Fluke 83 or
similar) and check resistance between test box
sockets 67 and 69.


Specified value: max. 5.0
- Open throttle slowly.


Specified value: If resistance is NOT OK:

- Disconnect 8-pin harness connector for throttle valve control module -
J338-.
- Check wiring for open circuit between ECM/test box and 8-pin harness
connector.

Connector terminal 3 to ECM/test box socket 69
Connector terminal 7 to ECM/test box socket 67
Specified value: max. 1.5
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- Press buttons -0- and -6- to select "End Output"
function 06, and press -Q- button to confirm
input.

- Switch ignition off.
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24-141

Continuation

- Switch ignition off.

- Connect VAG1598/22 test box to ECM harness
connector page 01
-67
.

- Switch ignition on.

- With throttle valve in closed throttle position,
connect multimeter US1119 (Fluke 83 or
equivalent), and check resistance between
ECM/test box sockets 59 and 66.


Specified value: 3-200 If resistance is NOT OK:

- Disconnect 8-pin harness connector from throttle
valve control module -J338-.

- Check wiring for open circuit between ECM/test box and 8-pin throttle
valve control module harness connector.

Connector terminal 1 to ECM/test box socket 66
Connector terminal 2 to ECM/test box socket 59
Connector terminal 7 to ECM/test box socket 67
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24-143

Throttle Position (TP) sensor, checking


Note:
The Throttle Position (TP) sensor -G69- is
located inside the throttle valve control module -
J338-.

Test conditions

Throttle valve in closed throttle position; if
necessary adjust accelerator pedal cable

Repair Manual, Fuel Supply System, Repair
Group 20


Cruise control adjustment OK
Power supply for throttle valve control
module OK; checking page 24
-130


Checking

- Connect VAG1551 or VAG1552 scan tool and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with ignition
switched; engine not running) page 01
-8 .
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24-144

- Press buttons -0-, -0- and -3- to input display
group number 3 (003), and press -Q- button to
confirm input. Read Measuring Value Block 3 1 2 3 4

Indicated on display (1-4 = display fields)
- Compare display with specified values for throttle angle, (display field
3):

Display fields

1 2 3 4
Display group 3: Load measurement
Display xxx RPM xx.x g/s
xxx
xx.x BTDC
Indicates Engine speed
(in 40 RPM
steps) Mass air
flow Throttle angle Ignition timing
Range 0 - 6800 RPM ---
0 - 90
0.0 - 50.0
BTDC
Specified
value 0 RPM ---
0 - 5
0.0

--- --- If not as specified page 24
-146
, Evaluation of
display group 3
---
-
Open throttle valve slowly while monitoring degree ( ) value in display field 3. Value must increase uniformly over the entire range.
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24-145

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

- Switch ignition off.

Note:
The values displayed in display field 3 depend on
the calibration of the Throttle Position (TP)
sensor and do not correspond with the actual
throttle valve opening in degrees. The maximum
displayed value is 90.0 . If the throttle angle value does not increase
uniformly:

- Replace throttle valve control module -J338-.

- Carry out adaptation of throttle valve control
module to ECM page 24
-150
.

- Check readiness code page 01
-70
. If
Diagnostic Trouble Code (DTC) memory has
been erased, or ECM was disconnected,
generate new readiness code page 01
-73
.
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