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

01-17

On Board Diagnostic (OBD) functions

A list of On Board Diagnostic functions can be
printed out by pressing the HELP button.
The following functions are available:

List of functions
Page
01 - Check Control Module
Versions Page 01
-8
02 - Check DTC Memory Page 01
-18


03 - Output Diagnostic Test
Mode Page 01
-42


04 - Basic Setting Page 01
-52


05 - Erase DTC Memory Page 01
-55


06 - End Output Page 01
-56


07 - Code Control Module Page 01
-57


08 - Read Measuring Value
Block Page 01
-63


Only the functions listed above can be used for
the "AC/Heating Electronics" OBD program.
Pa
ge 21 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1

01-20

If no DTC are displayed and A/C system
complaints exist (e.g. compressor does not
run or only occasionally, system control
unsatisfactory, speed of fresh air blower
cannot be regulated etc.):

- Read measuring value block (function 08).

- Perform Output Diagnostic Test Mode (DTM)
(function 03).

- Check A/C system cooling performance page
87
-213
.

- VAG1551 Scan Tool (ST) can be returned to the
function mode by pressing the button. Rapid data transfer
HELP
Select function XX

Indicated on display (function selection)
- End output (function 06) page 01
-56
.
- Switch ignition off and disconnect VAG1551 Scan Tool (ST) from Data
Link Connector (DLC).
Pa
ge 26 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1

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
.
Pa
ge 27 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1

01-23
Notes

If 22 C (72 F) is always displayed after switching ignition off and on, regardless of last setting, check power supply
(terminal 30) to A/C control head -E87- using wiring diagram. If a malfunction is recognized at an air/temperature distribution flap motor potentiometer, air distribution can be altered by
pressing buttons on A/C control head -E87-.
To switch display from C (Celsius) to F (Fahrenheit)(and vice versa), press "Temperature +" button while holding
"recirculating air" button. If no DTC are displayed and air conditioning system complaints exist (e.g. compressor does not run or only occasionally,
system control unsatisfactory, speed of fresh air blower cannot be regulated etc.), perform function 03 "Output Diagnostic
Test Mode (DTM)" and 08 "Read Measuring Value block."
Pa
ge 30 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1

01-24

VAG1551 scan tool
display Possible cause
Corrective action
00000
No DTC recognized If "no DTC recognized appears after performing repairs, OBD is ended.
00529 2122
Speed information
missing /SP1) - Open circuit in wiring between Engine Control Module
(ECM), instrument cluster and A/C control head -E87-
- ECM and instrument cluster supply an unusable engine
speed signal - Diagnose and repair open circuit in
wiring using wiring diagram
- Read measuring value block
page 01
-63

- Test engine speed signal
Repair Manual, Fuel Injection &
Ignition, Repair Group 24
00532 2234
Supply voltage

Signal too low /SP - Voltage drops in electrical system to levels of less than
9.5 V2)
- Contact resistance in cable connection to A/C
Refrigerant Low Pressure Switch -F73- - Test Generator (GEN) and Voltage
Regulator (VR)
Repair Manual, Engine
Mechanical, Repair Group 27
- Diagnose and repair contact
resistance using wiring diagram
1)This fault may be generated during Output Diagnostic Test Mode (DTM) (no engine speed signal recognized although A/C
compressor speed detected).
2) If voltage at -E87-connector -C3- drops below 9.5 V, compressor switches off for a minimum of 25 seconds. Compressor
switches on again when voltage exceeds 10.8 V.
Pa
ge 31 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1

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.
Pa
ge 34 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1

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.
Pa
ge 39 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1

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.
Pa
ge 40 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1

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.
Pa
ge 44 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1

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

Pa
ge 46 of 91 A/C s
ystem, On Board Dia
gnostic
(OBD
)
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.HA01.01.1