diagram AUDI A4 1998 B5 / 1.G AC System On Board Diagnostic User Guide

- Test road speed signal from
Speedometer G21 or from instrument
cluster (check all components
connected to this circuit using wiring
diagram)
1)This DTC only recognized during basic setting.
2)Both end stops must be reached.
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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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01-31

VAG1551 scan tool
display Possible cause
Corrective action
00801 3311
A/C Refrigerant High
Pressure Switch F118

Open circuit/short circuit to
positive /SP - Open circuit in wiring/connections between -F118-
and -E87-
- Malfunction in operation of coolant fan V7 (stage 1)


- Condenser or radiator dirty
- Malfunction of Coolant Fan V7 (stage 2) by A/C
Refrigerant High Pressure Switch F23
- -F23-/-F118-1) malfunction

- Refrigerant circuit malfunction- Diagnose and repair open circuit in
wiring using wiring diagram
- Test fan operation V7 (stage 1)
using
function 03 (Output DTM) page
01
-42

- -V7- electrical test page 01
-115
- Clean condenser and radiator
- Test V7 (stage 2) from -F23-
page 87
-64


- Test F23/F118 page 87
-64

(switching pressures)
- Check refrigerant system pressures
page 87
-192
.
1)F118 and F23 are integrated into the same housing.
Note:
If an open A/C Refrigerant High Pressure Switch -F118- was recognized 30 times during a driving period (e.g. because of a
loose contact), the compressor is switched off. Compressor can be switched on again by pressing "compressor on" button or
by switching ignition off and on. If this fault occurs over several driving periods, compressor cannot be switched on again until
DTC memory is erased.
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01-33

VAG1551 scan
tool display Possible cause
Corrective action
01270 4121
A/C Clutch N251)

Open circuit /SP












Continued on next
page - Short circuit or open circuit in wiring between A/C
compressor speed sensor -G111-2/3) and -E87-

- Open circuit in wiring between A/C Clutch Relay J44 and
N25
- Open circuit in voltage supply or in wiring/connections
between A/C clutch relay J44 and -E87-
- J44 malfunction
- N25 malfunction
- Malfunction in refrigerant circuit (A/C Compressor Speed
Sensor G111 not producing signals or compressor siezed2/3) - Diagnose and repair short or open
circuit in wiring using wiring diagram
- -G111- electrical test page 01
-
115

- Diagnose and repair open circuit
using
wiring diagram
- Diagnose and repair open circuit
using wiring diagram

- Replace -J44-
- Repair or replace -N25- page 87
-
85

- Replace -G111- page 87
-63
- Replace compressor page 87
-38
1)During m.y. 1996, Nippondenso type A/C compressors were installed as a running change. These compressors are not
equipped with A/C speed sensor G111. DTC at A/C Clutch -N25- are only detected only on compressors equipped with A/C
Compressor speed sensor G111.
2)Sender G111 produces 4 pulses for each compressor revolution.
3)A/C Clutch is switched on for a few seconds after engine starts.
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01-34

DTC 01270 continued
VAG1551 scan
tool display Possible cause
Corrective action
01270 4121
A/C Clutch N251)

Speed difference
too great /SP3)












Continued on
next page. - Ribbed belt loose, slipping



- A/C control head -E87- not coded correctly
- Loose terminal or contact resistance in circuit between
-N25- and A/C clutch relay -J44- or in wiring/connections
between -G111-2)4) and -E87-
- N25 slipping
- Incorrect crankshaft vibration damper (diameter)
- Malfunction in refrigerant circuit (compressor not
operating freely). - Check belt tension Repair Manual,
Engine Mechanical, Repair Group 13
Compare speeds of engine and compressor
using function 08 (Read measuring value
block) page 01
-63

- Code A/C control head -E87- according to
compressor type installed4) "Zexel" or
"Nippondenso" page 01
-57

- Diagnose and repair circuit using wiring
diagram and perform electrical tests
page 01
-115

- -G111-, -J44- electrical test page 01
-
115

- Repair or replace -N25- page 87
-85
- Check for proper vibration damper part
number
- Check compressor for free operation and
replace if necessary page 87
-38

1/2) Continued from page 01
-33

3) If speed difference is 30 % to 60 %, A/C Clutch is switched on again by -E87- for not more than 9 times during a driving
period (ignition off). If speed difference is greater than 60 %, A/C Clutch remains off until engine is started again.
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01-35

DTC 01270 continued
VAG1551 scan tool
display Possible cause
Corrective action
01270 4121
A/C Clutch N251)

Mechanical
malfunction /SP2) - Belt and coupling pulley of -N25- are stuck together
- Short circuit to positive in wiring/connections between -
N25- and for A/C Clutch relay -J44-
- -J44- malfunction
- Short circuit to ground in wiring/connections between -E87-
and -J44- - Repair or replace -N25-
page 87
-85


- Diagnose and repair short
circuit using
wiring diagram

- Replace -J44-
- Diagnose and repair short
circuit using
wiring diagram.
01271 4122
Temperature Regulator
Flap Motor V68

Blocks or de-energized
/SP - Short circuit, open circuit or incorrect terminal assignment
(wires interchanged) of connectors between -V68- and -E87-
- Temperature flap sticking
- -V68- malfunction- Diagnose and repair short
circuit, open
circuit or confirm terminal
assignment using wiring
diagram
- Check for free operation of
temperature flap
- Test -V68- using function 03
(Output DTM)
page 01
-42

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01-36

VAG1551 scan tool
display Possible cause
Corrective action
01272 4123
Central Air Flap
Motor -V70-

Blocks or de-
energized /SP - Short circuit, open circuit in wiring or incorrect terminal
assignment (wires interchanged) of connectors between -
V70- and -E87-
- Central flap sticking
- -V70- malfunction- Diagnose and repair short circuit,
open
circuit or confirm terminal assignment
using wiring diagram
- Check for free operation of central
flap
- Test -V70- using function 03 (Output
DTM)
page 01
-42

01273 4124
Fresh air blower V2

Control
difference /SP - Short circuit or open circuit in wiring between V2, control
module for fresh air blower J126 and/or -E87-
- Open circuit in voltage supply or ground connection to -
J126-
- -J126- malfunction
- -V2- mechanical malfunction.- Diagnose and repair short circuit or
open circuit in wiring using wiring
diagram

- Diagnose and repair open circuit
using
wiring diagram
- -J126- electrical test page 01
-115
- Replace -V2-
01274 4131
Air flow flap motor
V71
- Short circuit, open circuit in wiring or incorrect terminal
assignment (wires interchanged) of connectors between
V71 and -E87-
- Air flow flap sticking- Diagnose and repair short circuit,
open
circuit or confirm terminal assignment
using wiring diagram
Pa
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01-37

VAG1551 Scan Tool display
Possible cause
Corrective action
01582
Coolant Temperature Signal
Short circuit or open circuit between
instrument cluster and A/C control head -
E87- - Locate short circuit or open circuit
according to wiring diagram and repair
Short circuit to
Ground /SP
Open/Short circuit
to B+ /SP
Incorrect
Signal /SP Instrument cluster malfunctioning- Check signal from instrument cluster.
Note:
The DTC "Coolant Temperature Signal" is only recognized by A/C control heads -E87- with one display.
Pa
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