1998 AUDI A4 transmission

24-90

A/C compressor shut-off signal,
checking


Note:
The A/C compressor is switched off during
acceleration by the Engine Control Module
(ECM) and at wide open throttle by the
Transmission Control Module (TCM) via the
kickdown switch.
A/C compressor shut-off is bi-directional ("in"and
"out").

IN: Shortly before switching the A/C
compressor on, voltage is applied to the ECM
which causes the Idle Air Control (IAC) valve to
open a little more to adjust to the higher load.
OUT: When accelerating from a standstill
position and at lower speed, the A/C
compressor is shut off for approx. 12 seconds
via control by the ECM. If the accelerator pedal
is released early enough, the duration is
reduced to a minimal 3 seconds.

Checking requirements
A/C function OK

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24-92
If the specified values are obtained:

-
Press button.
- Select "End Output" function 06.

- Press -Q- button to confirm input.
If display value changes:

- The following display is possible: "A/C system
not switched on as described."
If the display value does not change, even
though the A/C system was switched on as
described:

If wiring is OK:
Repair Manual, Heating & Air Conditioning, Repair Group 01; connect VAG 1551 scan tool and select "Check DTC Memory" function 02

Repair Manual, 5 Spd. Automatic Transmission 01V, Repair Group 01;
connect VAG 1551 scan tool and select "Check DTC Memory" function 02
- Check wiring for continuity between connector terminal C11 and ECM
or TCM using wiring diagram.
- Check A/C system or automatic transmission:
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24-93
If X1X_XX is displayed:

- Briefly press accelerator pedal to apply wide
open throttle.

Display must switch briefly to X0X_XX, then
X1X_XX must appear again after several
seconds.
If display does not change as described:

- Check whether A/C compressor was shut off
while accelerator pedal was being pressed.

- Check A/C system or automatic transmission.

Repair Manual, Heating & Air Conditioning,
Repair Group 01; connect VAG 1551 scan tool and select "Check DTC Memory" function 02


Repair Manual, 5 Spd. Automatic
Transmission 01V, Repair Group 01
; connect
VAG 1551 scan tool and select "Check DTC
Memory" function 02
If the display does not change as described:
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24-94

Engine speed (RPM) signal, checking


Notes:
The RPM signal is routed from the ECM to
various electronic systems (e.g. automatic
transmission, ABS, etc.). The RPM signal is
monitored by the different electronic systems.
Carry out the following check only if the
tachometer (in the instrument cluster) is
inoperative, or if the A/C compressor is not
running.

- Connect VAG 1367 engine-tester to tachometer
using wiring diagram.

- Connect VAG 1367 engine-tester signal wire
(green terminal) to instrument cluster RPM
terminal and A/C control module RPM terminal
(connector remains connected).

- Start engine and let idle.

RPM must be displayed again
If the specified value is obtained, the malfunction
is in instrument cluster or on A/C control module.
If the RPM is not displayed on VAG 1367 engine-
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24-95

Fuel consumption signal, checking


Notes:

The consumption signal is internally calculated
by the ECM using "injection time."
The consumption signal is routed to both the
trip computer and the Transmission Control
Module (TCM).
The consumption signal is monitored by the
TCM

Repair Manual, 5 Spd. Automatic
Transmission 01V, Repair Group 01; On Board Diagnostic

Carry out the following check only if DTC
memory contains a stored DTC for the TCM
related to the consumption signal, or a missing or
false consumption signal, determined during the
trip computer check.

- Remove instrument cluster or TCM.

Repair Manual, Electrical Equipment, Repair
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Group 90; Instrument cluster, repairing


Repair Manual, 5 Spd. Automatic
Transmission 01V, Repair Group 01, On Board Diagnostic


- Connect VAG 1598 test box to instrument
cluster harness connector (I/P insert not
connected) or to TCM harness connector (TCM
not connected).

Repair Manual, Electrical Equipment, Repair
Group 90; Instrument cluster, repairing


Repair Manual, 5 Spd. Automatic
Transmission 01V; Repair Group 01, On Board Diagnostic

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24-97

Vehicle speed signal, checking


Note:
The vehicle speed signal originates from the
vehicle speed sensor (on the transmission) and
is routed to the instrument cluster as well as to
the Engine Control Module (ECM).

Speedometer in instrument cluster OK

Checking

- Using VAG 1551 scan tool, select "Read
Measuring Value Block" function 08, display
group 003 page 01
-249
.
Read measuring value block 3 1 2 3 4

Indicated on display
- Observe display field 4 while accelerating from standstill.
Specified values:

0 mph (at standstill)
Actual speed (vehicle driven)
-
Press button.
- Select "End Output" function 06.
- Press -Q- button to confirm input.
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24-99

Transmission Range (TR) selector lever
position signal, checking


Note:
The Engine Control Module (ECM) uses this
signal to recognize the transmission range
selector lever position. When a driving mode is
selected, idle speed should drop by approx. 50
RPM to reduce creep.

Checking requirement

Control module coding OK page 01
-247
.

- Switch ignition ON.

- Using VAG 1551 scan tool, select "Read
Measuring Value Block" function 08, display
group 004, display field 4 page 01
-249
.
Read measuring value block 4 1 2 3 4

Indicated on display
CAUTION! Specified value: XXX_1X (TR selector lever in P or N)
- Apply brake and select drive mode (1, 2, 3, R or D).
Specified value: XXX_0X
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