AUDI A6 1999 C5 / 2.G AEB Engine Additional Signal

24-145


Additional signals

Signal from A/C compressor, checking


Required special tools and test equipment

VAG 1551 or VAG 1552 Scan Tool (ST) with
VAG 1551/3 adapter cable
VAG 1598/22 test box
Multimeter US 1119 (Fluke 83 or equivalent)
VW 1594 connector test kit
Wiring diagrams

Test conditions
A/C functions OK
A/C is switched off
Vehicle at room temperature-above 15 C
(59 F)

No malfunctions stored in Diagnostic Trouble
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Code (DTC) memory Page 01
-15
.
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24-146

Checking

- Connect VAG 1551 or VAG 1552 scan tool and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with engine
running at idle) Page 01
-7 .
Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block"
function 08, and press -Q- button to confirm input.
Read Measurin
g Value Block
HELP
Input displa
y group number XXX

Indicated on display
- Press buttons -0-, -5- and -0- to input display group number 50, and
press -Q- button to confirm input.
Read Measuring Value Block 50 1 2 3 4

Indicated on display (1-4 = display fields)
- Switch on A/C (lowest temperature and highest fan position).
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24-147

- Compare display with specified value in display
field 4.

Display fields

1 2 3
4
Display group 50: Signals to Engine Control Module (ECM)
Display xxxx RPM xxxx RPM A/C-LOW
Compr. ON
Compr. OFF
Indicates Actual engine
speed
(in 10 RPM steps) Specified engine
speed
(in 10 RPM steps) A/C
status A/C compressor status
Range 0-2550 RPM ---
---
Specified
value 820-900 RPM 860 RPM A/C-LOW
Compressor on: Compr. On
Compressor off: Compr. OFF

--- --- ---
If not as specified Page 24
-148
,
Continuation

Notes:

The A/C compressor is switched off during
acceleration when the car is stationary or at
slow speed.

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At wide open throttle the A/C compressor is
switched off by the Transmission Control
Module (TCM) (kick down switch).
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24-148

Continuation
If the displayed values are NOT OK:

- Connect VAG 1598/22 test box to ECM harness
connector Page 01
-56
.

- Check wiring for open circuit, short circuit to B+
or short circuit to Ground between ECM/test box
terminal 8 and A/C control head -E87-, or
Transmission Control Module (TCM).

Electrical Wiring Diagrams, Troubleshooting &
Component Locations If the wiring is OK:

- Check function of A/C control head -E87-.

Repair Manual, Heating & Air Conditioning,
Repair Group 01

Or:

Repair Manual, 5 Spd. Automatic
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Transmission 01V, Repair Group 01


- Check readiness code Page 01-59
. If
Diagnostic Trouble Code (DTC) memory has
been erased, or ECM was disconnected,
generate new readiness code Page 01
-62
.
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24-149

Vehicle speed signal, checking


Required special tools and test equipment

VAG 1551 or VAG 1552 Scan Tool (ST) with
VAG 1551/3 adapter cable
Multimeter US 1119 (Fluke 83 or equivalent)
VW 1594 connector test kit
Wiring diagrams

Test conditions
Vehicle Speed Sensor (VSS) OK; checking:

Repair Manual, Electrical Equipment, Repair
Group 90


Notes:

To check Vehicle Speed Sensor -G68-, the
vehicle must be driven. A second technician is
required to operate the scan tool during the
road test.
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The speed signal is generated by the vehicle
speed sensor (at the transmission), and
processed at the speedometer/odometer in the
instrument cluster.
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24-150

Test procedure

- Connect VAG 1551 or VAG 1552 scan tool and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with engine
running at idle) Page 01
-7 .
Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -8- to select "Read Measuring Value Block"
function 08, and press -Q- button to confirm input.
Read Measurin
g Value Block
HELP
Input displa
y group number XXX

Indicated on display
- Press buttons -0-, -0- and -5- to input display group number 5, and
press -Q- button to confirm input.
Read Measuring Value Block 5 1 2 3 4

Indicated on display (1-4 = display fields)
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