1999 AUDI A4 ignition

01-46
Output Diagnostic Test Mode (DTM) table

VAG1551 scan tool display
Specified function
Corrective action
A/C Clutch N25








Notes: - N25 clicks every 2-seconds
- Output of A/C control head -E87- is switched from 0 V to
12 V every 2-seconds2) - Test voltage supply for -
N25- (via A/C Clutch
Relay J44) using wiring
diagram
- Repair or replace -N25-
page 87
-90

- Test circuit and
connectors between A/C
control head -E87-, J44
and -N25- using wiring
diagram
- Replace -E87-

"A/C compressor on" output to
Engine Control Module (ECM)
and -E87- terminal -C12- is
also actuated at the same
time1)
Output of -E87- switched from 0 V to 12 V every 2
seconds can be confirmed by switching compressor on
and off using the "ECON" button while reading the
measured value block of engine control module
Repair Manual, Fuel Injection and Ignition System,
Repair Group 01)

1)Test this "A/C compressor on" signal only if complaints exist. ECM uses signal to compensate for engine load when
compressor engages Repair Manual, "Fuel Injection & Ignition," Repair Group 24 . ECM is capable of switching off the A/C compressor from this signal. Confirm via function 08, Read measuring value block,
page Page 01
-63
, display group 01 and Fuel Injection and Ignition System Repair Manual, Repair group 01: Read
measured value block of ECM with engine running and at same time switch compressor on and off.
Pa
ge 65 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

01-55

Erase DTC Memory (function 05)


Requirements

DTC Memory checked

Erasing DTC memory

-
Press button.
Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -5-.
Rapid data transfer
Q
05 - Erase DTC Memor
y

Indicated on display
- Press -Q- button to confirm input.
Rapid data transfer
Q
DTC Memor
y is erased!

Indicated on display
-
Press button.
Attention!DTC Memor
y is not interro
gated

Indicated on display
Notes:
If display appears as shown, check DTC memory and follow test
procedures carefully page 01
-18
.
If ignition was switched off between "Check DTC Memory" and "Erase
DTC memory," the memory is not erased. Check DTC memory once
Pa
ge 77 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

Enter address word XX
- Switch ignition off and disconnect VAG1551 Scan Tool (ST) from Data
Link Connector (DLC).
Pa
ge 80 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

01-57

Code Control Module (function 07)


A/C control head -E87- coding, vehicles 1996

Notes:

A/C control head coding 1997 page 01
-
59
.

A/C control head coding 1998 page 01
-
61
.
A/C control head -E87- coding shows market
application, compressor type and engine type.

Notes:

Zexel A/C compressors are 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.
Each time A/C control head -E87- is coded,
basic setting must be performed page 01
-
52
.

If a the display of a newly installed A/C control
head -E87- flashes after switching ignition on
(for approximately 2 minutes), code the control
Pa
ge 81 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