light AUDI A4 2000 B5 / 1.G AFC Engine Auxiliary Input Signals Checking Workshop Manual

24-89
If display value does not change:

- Switch ignition OFF and connect VAG 1598/19
test box to ECM harness connector page 01
-
255
.

- Connect VAG 1527B voltage tester between
VAG 1598/19 test box socket C14 and Ground
(GND).

- Switch ignition ON.

- Switch ON rear window defroster.

Voltage tester must light up
If voltage tester does not light up:

If wiring is OK:
If rear window defroster is OK: - Check wiring for continuity between C14 and rear window defroster
using wiring diagram.
- Check rear window defroster using wiring diagram.
- Replace ECM page 01
-265
.
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24-91

Checking

- Start engine and let idle.

- Switch A/C on, push "AUTO" button, set
temperature to "LO" and blower speed to "HI".

A/C compressor symbol must light up and
A/C must run.

- Using VAG 1551 scan tool, select "Basic
Setting" function 04, display group 004 page 01
-150
.

A/C compressor must stop (visual check)
If the A/C compressor does not shut off:

- Switch A/C off (press "minus" button for fresh air
blower in A/C control head repeatedly, until all
indicators are off).

Continue to let engine run in idle.

- Using VAG 1551 scan tool, select "Read
Measuring Value Block" function 08, display
group 004.
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24-98
If no vehicle speed is displayed between
standstill and moving:

- Switch ignition OFF and connect VAG 1598/19
test box page 01
-255
.

- Connect VAG 1527B voltage tester between test
box sockets 13C (signal) and 10D (B+).

- Raise front of vehicle until left-front wheel is free
to rotate.

Note:
The right front wheel must NOT rotate.

- Switch ignition ON.

Voltage tester must light up at half strength

- Rotate left front wheel by hand.
Voltage tester must become brighter (flash)
If tester does not light up (become brighter) or
flash:

-
Check wiring between test box socket 13X and
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vehicle speed sensor, using wiring diagram.

If wiring is OK, replace vehicle speed sensor.
If voltage tester does not light up (become brighter) or flash, replace ECM
page 01
-265
. - Find and eliminate open circuit in wiring between terminal C13 and
vehicle speed sensor.
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24-100

-
Press button.
- Select "End Output" function 06 and press -Q-
button to confirm input.
If a display did NOT change, even though coding
is OK:

- Connect VAG 1598/19 test box to ECM harness
connector page 01
-255
.

- Connect VAG 1527B voltage tester between test
box sockets 11B (signal) and 10B (constant
B+/terminal 30).

Voltage tester must light up (with TR selector
lever in P or N), then go out with drive mode
(1, 2, 3, R or D) selected
If voltage tester lights up and goes out when
drive mode is selected, even though the range
indicator in the "Read measuring value block" is
OK:

- Replace ECM page 01
-265
.
If voltage tester lights up constantly or not at all:

-
Check wiring for short to ground, short to B+ or open circuit between
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24-110

- Find and eliminate open or short circuit; repair
as necessary.
If wiring is OK:

- Replace ABS control module.
If the ABS control module is OK, but the
malfunction is still occurring:

- Replace ECM page 01
-265
.

ABS control module with ABS/EDL/ASR

Notes:

The torque signal is monitored by the
"Automatic Traction Control" Control Module
and by the ECM.

Repair Manual, Brake System On Board
Diagnostic (OBD), Repair Group 01


Vehicles with automatic traction control (ASR)
can be recognized by the ASR indicator light in
the instrument cluster or by control module
identification displayed during the ABS On
Board Diagnostic program sequence.
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