sensor AUDI A4 1998 B5 / 1.G AC System On Board Diagnostic Workshop Manual

01-1


A/C system, On Board
Diagnostic (OBD)

Function
The A/C control head -E87- receives input
information from various electrical and electronic
components (sensors).
This information is processed by the control head
in accordance with specified values and then
provides corresponding output signals that
control electrical components (actuators).
The control head is controlled by an internal
microprocessor with On Board Diagnostic (OBD)
capability. If faults or open circuits occur on
applicable components, Diagnostic Trouble
Codes (DTC) are stored in DTC memory. Stored
faults are identified using either VAG1551 Scan
Tool (ST) or VAG1552 Scan Tool (ST). Tables
containing all DTCs and corresponding repair
information guide technicians through the OBD
process.
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temperature sensor are used as instantaneous
outside and engine temperature inputs for A/C
system control. If "standing time" is shorter than
4 hours, the actual measured values of the
outside temperature sensor are suppressed
and system output temperature control is
calculated by the A/C control head. The
"standing time" period is monitored and used
for this calculation. (Heat radiating from the
engine and radiator leads affects the measured
value of the temperature sensor).
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01-15

Notes:

Zexel A/C compressors were installed from
start of production. During m.y. 1996,
Nippondenso type compressors are installed as
a running change. These compressors are not
equipped with A/C speed sensor G111.
The A/C control head is coded to reflect the
compressor type installed (Zexel or
Nippondenso).
Vehicles equipped with Nippondenso (Denso)
compressors must have A/C control head with
Part No. index "H" or higher installed to allow
for correct coding.
Follow coding exactly when replacing an A/C
control head -E87-.

Parts catalog microfiche

A/C control head varies after VIN 200000 of
m.y. 1999 for vehicles with and without radio
navigation system (or a radio with a large
control panel), with and without switch for
heated seats (e.g. index "M", "N", "P" or "Q").
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01-21

Notes:

1997 If A/C control head -E87- is unable to
determine the duration of time when ignition is
off ("standing time"), DTC 01206 "signal for time
span ignition off" is loaded into memory. The
A/C control head will then default to a standing
time greater than 4 hours. The actual measured
values of the outside temperature sensor are
then used as instantaneous outside and engine
temperature inputs for A/C system control.
When the "heating" mode is selected under
these conditions, fresh air blower -V2- has a
delayed start (even when the actual standing
time is less than 4 hours and the engine is
warm) page 01
-86
, Read Measuring Value
Block. The outside air temperature display -
G106- may also indicate incorrect outside
temperature values.

If both display fields of the A/C control head do
not light with ignition switched on check control
head coding Page 01
-57
.
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01-25

VAG1551 scan tool display
Possible cause
Corrective action
00600
Temperature Regulator Flap Motor
Position Sensor -G92- for
Temperature Regulator Flap Motor
V681)
Short circuit to ground /SP

Open circuit/short circuit to
positive /SP
Adaptation limit exceeded
Mechanical malfunction. - Short circuit, open circuit in wiring or
incorrect terminal assignment (wires
interchanged) of connectors between -G92-
and -E87-
- Temperature flap not operating freely
- -G92- in -V68- inoperative- Diagnose and repair short circuit,
open circuit in wiring or confirm
terminal assignment using wiring
diagram

- Check for free operation of
temperature flap
- Replace -V68-
00601
Central Flap Motor Position Sensor
G112 in Central Air Flap Motor V70
Short circuit to ground /SP

Open circuit/short circuit to
positive /SP
Adaptation limit exceeded2)
Mechanical malfunction - Short circuit, open circuit in wiring or
incorrect terminal assignment (wires
interchanged) of connectors between -
G112- and -E87-
- Central flap not operating freely
- -G112- in V70 inoperative- Diagnose and repair short circuit,
open circuit in wiring or confirm
terminal assignment using wiring
diagram

- Check for free operation of central
flap3)
- Replace -V70-
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01-26

VAG1551 scan tool display
Possible cause
Corrective action
00602
Footwell/Defrost Flap Motor
Position Sensor G114 in
Footwell/Defroster Flap Motor V85
Short circuit to ground /SP

Open circuit/short circuit to
positive /SP

Adaptation limit exceeded1)

Inoperative - Short circuit, open circuit in wiring or
incorrect terminal assignment (wires
interchanged) of connectors between -G114-
and -E87-
- Footwell/defroster flap not operating freely
- -G114- in -V85- inoperative- Diagnose and repair short circuit,
open circuit in wiring or confirm
terminal assignment using wiring
diagram

- Check for free operation of
footwell/defroster flap2)
- Replace -V85-
00603
Footwell/Defroster Flap Motor V85

Blocks or de-energized /SP - Short circuit, open circuit in wiring or
incorrect terminal assignment (wires
interchanged) of connectors between V85
and -E87-
- Footwell/defroster flap flap not operating
freely
- -V85- inoperative- Diagnose and repair short circuit,
open circuit in wiring or confirm
terminal assignment using wiring
diagram

- Check for free operation of
footwell/defroster flap
- Check -V85- using function 03
(Output DTM) page 01
-42

1)This fault only recognized during basic setting.
2) Both end stops must be reached.
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01-27

VAG1551 scan tool
display Possible cause
Corrective action
00604
Back Pressure Flap
Motor Position Sensor
G113 in Air Flow Flap
Motor V71

Short circuit to
ground /SP

Open circuit/short
circuit to positive /SP

Adaptation limit
exceeded1)

Inoperative - Short circuit, open circuit in wiring or incorrect terminal
assignment (wires interchanged) of connectors between -
G113- and -E87-
- Air flow flap not operating freely
- -G113- in -V71- inoperative- Diagnose and repair short circuit,
open circuit in wiring or confirm
terminal assignment using wiring
diagram

- Check for free operation of air flow
flap2)
- Replace -V71-
00625
Road speed signal

Implausible signal /SP - Loose terminal in wiring/connections between
Speedometer Vehicle Speed Sensor (VSS) G22, the
instrument cluster or in another component also
connected to this signal (e.g. radio or control module for
cruise control) and -E87-
- Speedometer -G21- or instrument cluster supplying
unusable signal or a component disrupts signal - Diagnose and repair loose terminal
using wiring diagram.





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01-28

VAG1551 scan tool display
Possible cause
Corrective action
00779 3133
Outside Air Temperature Sensor G17

Short circuit to ground /SP

Open circuit/short circuit
to positive /SP - Short circuit or open
circuit
between -G17- and -
E87-
- -G17- malfunction- Diagnose and repair short circuit or open circuit in
wiring using wiring diagram
- -G17- electrical test page 01
-115
00785 3211
Instrument Panel Interior Temperature
Sensor G56

Short circuit to ground /SP

Open circuit/short circuit to
positive /SP - Short circuit or open
circuit
between -G56- and -
E87-
- -G56- malfunction- Diagnose and repair short circuit or open circuit using
wiring diagram
- -G56- electrical test page 01
-115
00787 3213
Fresh Air Intake Duct Temperature
Sensor G89

Short circuit to ground /SP
- Short circuit or open
circuit
between -G89- and -
E87-
- -G89- malfunction- Diagnose and repair short circuit or open circuit in
wiring using wiring diagram
- -G89- electrical test page 01
-115
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01-29

VAG1551 scan tool display
Possible cause
Corrective action
00797 3241
Sunlight Photo Sensor G107

Open circuit/short circuit to positive /SP

Short circuit to ground /SP - Short circuit or open
circuit
between -G107- and -
E87-
- Connections to -
G107-
interchanged
- -G107- malfunction- Diagnose and repair short circuit or open circuit in
wiring using wiring diagram
- Confirm connection using wiring diagram

- Test G107 using function 08
(Read measuring value block) page 01
-63
- Replace -G107-
00799 3243
A/C Engine Coolant Temperature (ECT)
Sensor G1101)

Open circuit/short circuit to positive /SP

Short circuit to ground /SP - Short circuit or open
circuit
between -G110-1) and
-E87-
- -G110-1) malfunction- Diagnose and repair short circuit or open circuit in
wiring using wiring diagram
- Test -G110-1) using function 08
(Read measuring value block)
page 01
-63

1) Not on USA/CDN models.
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01-30

VAG1551 Scan Tool display
Possible cause
Corrective action
00785 3211
Instrument panel
interior temperature
sensor
-G56
Short circuit or open circuit between
instrument panel interior temperature
sensor -G56- and A/C control head -E87- - Locate short circuit or open
circuit using wiring diagram and
repair
Short circuit to
Ground /SP
Open/Short
circuit to B+ /SP Instrument panel interior temperature
sensor -G56- malfunctioning - Check instrument panel interior
temperature sensor -G56-
electrical testing, page 01
-115

Note for DTC 00785:
For the A/C control head -E87-, the instrument panel interior temperature sensor -G56- is installed with only one display in the
A/C control head -E87-. instrument panel interior temperature sensor-G56- cannot be checked or replaced individually, if
malfunctioning replace A/C control head -E87- completely. VAG1551 Scan Tool display
Possible cause
Corrective action
00796 6) 3234
Interior temperature
sensor fan-V42
Open circuit in power supply to -V42- or in
wiring connection between -V42- and -E87- - Locate and repair open
circuit using wiring diagram
Blocked or no
voltage /SP Interior temperature sensor fan -V42-
malfunctioning - Replace A/C control head -
E87-
6) For an A/C control head -E87- with only one display, the interior temperature sensor fan -V42- is installed in the A/C control
head -E87-; if malfunctioning replace complete unit.
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