AUDI A6 1996 C5 / 2.G ATQ Engine Additional Signals Testing User Guide

24-174

- Depress gas pedal completely (swiftly) and then
release it (brief acceleration).


Specified value in display field 4: Indication
jumps for a few seconds from "Compr. ON"
to "Compr. OFF" (compressor is switched off
when vehicle accelerates).
If indications do not resemble description:

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM Page 24
-17
.

- Check the following wire connection for open
circuit and short circuit to Ground (GND) and B+:

Test box
VAG1598/31
Socket
A/C control
head -E87-
Terminal
41 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations binder

- Repair open circuit or short circuit if
necessary.

Pa
ge 11 of 44 Additional si
gnals, testin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.6

- If there are no malfunctions in the wiring, check
function of A/C system.

Repair Manual, Heating & Air Conditioning, Repair Group 01

Pa
ge 12 of 44 Additional si
gnals, testin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.6

24-175

A/C system signal, checking

The A/C system signal notifies the Engine
Control Module (ECM), that the A/C system
requires a higher idle speed to achieve the
desired interior temperature (regardless of
whether heating or cooling is required).
The increase in idle speed based on presence of
the A/C system signal is control module
dependent and occurs only in vehicles with All
Wheel Drive (AWD) and manual transmission.

Test sequence

- Connect VAS5051 tester or VAG1551 scan tool
and select the control module for engine
electronics using "address word" 01 Page 01
-
9 .

Engine must run at idle for this.Rapid data transfer
HELP
Select function XX

When indicated on display:
- Press buttons -0- and -8- to select "Read Measuring Value Block" and
press -Q- button to confirm input.
Pa
ge 13 of 44 Additional si
gnals, testin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.6

24-176
If specified values are not obtained:
Read Measuring Value Block
Q
Input displa
y group number XXX

When indicated on display:
- Press buttons -0-, -5- and -6- to select "display group number 056" and press -Q-
button to confirm input.
- Switch on A/C system, press "Auto" button and select the lowest temperature.
- Check indications in display field 3 and 4.

Display fields

1 2 3 4
Display group 056: Idle stabilization with engine at idle and operating temperature
Display xxx /min xxx /min
---
---
Indicated Engine speed (actual) Engine speed (specified)
A/C readiness
A/C compressor
Functional range

A/C - LOW
A/C - HIGH Compr. OFF
Compr. ON
Specified value
720 to 820 RPM
1)
630 to 730 RPM 2) 760 RPM
1)
680 RPM 2) A/C - HIGH
Compr. ON
1) Front Wheel Drive Vehicles 2) All-Wheel Drive Vehicles
- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM Page 24
-17
.
Pa
ge 14 of 44 Additional si
gnals, testin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.6

24-177

- Check the following wire connection for open
circuit and short circuit to Ground (GND) and B+:

Test box
VAG1598/31
Socket
A/C control
head -E87-
Terminal
40 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations binder

- Repair open circuit or short circuit if
necessary.

- If there are no malfunctions in the wiring, check
function of A/C system.

Repair Manual, Heating & Air Conditioning,
Repair Group 01

Pa
ge 15 of 44 Additional si
gnals, testin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.6

24-178

Brake light switch and brake pedal
switch, checking


Note:
For safety reasons, the instruction from the
accelerator pedal sensor (potentiometer) to the
ECM to open the throttle valve is suppressed
when brake is being operated. This requires the
brake light switch signal and also the brake pedal
switch signal in the control module.
If brake pedal is operated with accelerator pedal
constantly depressed, engine is immediately
regulated down to idle speed. A faulty switch can
lead to undesired regulation.

Test sequence

- Connect VAS5051 tester or VAG1551 scan tool
and select the control module for engine
electronics using "address word" 01 Page 01
-
9 .

Ignition must remain switched on for this.Rapid data transfer
HELP
Select function XX

When indicated on display:
- Press buttons -0- and -8- to select "Read Measuring Value Block" and
press -Q- button to confirm input.
Pa
ge 16 of 44 Additional si
gnals, testin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.6

24-179

Read Measurin
g Value Block
Q
Input display group number XXX

When indicated on display:
- Press buttons -0-, -6- and -6- to select "display group number 066" and
press -Q- button to confirm input.
Read Measuring Value Block 66
1
2
3
4

Indicated on display:
- Check brake light/brake pedal switch in display field 2.

Display fields

1 2 3 4
Display group 066: Signals to Engine Control Module (ECM)
Display xxx km/h
XXXX xxx km/h XXXX
Indicated ACTUAL speed
Switch positions SPECIFIED speed Switch positions
Functional range
XX00
XX11
Specified value
XX00
(with brake pedal
not operated)

XX11
(with brake pedal
operated)
Notes
Value:
X = no significance.
Pa
ge 17 of 44 Additional si
gnals, testin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.6

Switch points slightly offset
Pa
ge 18 of 44 Additional si
gnals, testin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.6

24-180
If indications do not resemble description:

Check switch

- Remove driver-side storage compartment.

Repair Manual, Body
-Interior, Repair Group
68; Instrument Panel; Removing Driver
-Side
Storage Compartment


- Disconnect harness connector at brake light
switch and brake pedal switch.

Note:
Connector sockets are marked on the back side
of the connector.

- Connect multimeter between terminal 1 and 2 for resistance
measurement.

Specification: (no continuity)
- Depress accelerator pedal.

Specification: approx. 0
- Connect multimeter between terminal 3 and 4 for resistance
measurement.

Specification: approx. 0
Pa
ge 19 of 44 Additional si
gnals, testin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.6

- Depress accelerator pedal.

Specification: (no continuity)
Pa
ge 20 of 44 Additional si
gnals, testin
g
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU05.24.6