display AUDI A8 1998 D2 / 1.G AEB Engine Motronic MFI And Ignition System

24-72
Evaluation of display group 4 Display group: 4


Display field: 4
Possible cause
Corrective action
-46.5 C
Open or short circuit in wiring to B+ Page 24
-72
, check wiring
141.0 C
Short circuit to ground
approx. ambient temperature Signal intermittently interrupted
Continuation of test, page Page 24
-74
- Check IAT sensor

Wiring, checking:

- Switch ignition off.

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

- Disconnect 2-pin connector from Intake Air
Temperature (IAT) sensor -G42-.

- Check wiring for open circuit between ECM/test box and 2-pin IAT harness
connector (to ECM).

Connector terminal 1 to ECM/test box socket 54
Connector terminal 2 to ECM/test box socket 67
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24-74

Continuation of test
(when IAT sensor indicates approx. ambient
temperature)

- Without disconnecting harness connector,
remove IAT sensor -G42-.

- Monitor intake air temperature value in display
field 4.

- Spray sensor with commercially available
chilling spray and check temperature value in
display field 4.

Temperature value must decrease
If NOT:

- Replace intake air temperature sensor -G42-.

- 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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24-77

Voltage supply to Engine Control
Module (ECM)


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 diagram

Checking

- Connect VAG 1551 or VAG 1552 scan tool and
press buttons -0- and -1- to insert "Engine
Electronics" address word 01 (with ignition
switched on) 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.
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Read Measurin
g Value Block
HELP
Input display group number XXX

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

Indicated on display (1-4 = display fields)
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24-78

- Check battery positive voltage (B+) in display
field 2.

Display fields

1 2 3 4
Display group 4: Basic engine setting
Display xxx RPM xx.xxx V
xxx.x C
xxx.x 5C
Indicates Engine speed
(in 40 RPM
steps) Battery Positive Voltage (B+) Engine coolant
temperature Intake air
temperature
Range 0-6800 RPM 0.000-16.500 V -46.5 to 141.0 -46.5 to 141.0
Specified
value 0 RPM 10.000-14.500 V --- ---

--- If not as specified Page 24
-79
, Evaluation
of display group 4
--- ---
If displayed value is OK (as specified):

-
Press button to advance program
sequence.
- Press buttons -0- and -6- to select "End Output"
function 06, and press -Q- button to confirm
input.
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24-79
Evaluation of display group 4 Display group: 4


Display field: 2
Possible cause
Corrective action
No VAG 1551 display
Fuse for ECM faulty- Replace fuse
Open circuit in wiring- Voltage supply at terminal 15 Page 24
-
80

Displayed value changes between 10.0-14.5
V
Intermittent connection - Voltage supply at terminal 30 Page 24
-
79

0.0-10.0 V
Battery
discharged/faulty Voltage regulator faulty - Check battery
- Check generator
- Check voltage regulator
14.5-16.5 V Generator faultyVoltage regulator faulty - Check generator
- Check voltage regulator

Checking voltage supply at terminal 30

- Switch ignition off.

- Connect VAG 1598/22 test box to ECM harness
connector Page 01
-56
.
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24-97

Intake air system, checking for leaks
(false air)


Required special tools and test equipment

VAG 1551 or VAG 1552 Scan Tool (ST) with
VAG 1551/3 adapter cable
Engine leak detector spray G 001 800 A1

Notes:
If there are leaks, intake manifold vacuum will
draw in the leak detector spray with outside air.
The spray reduces the ability of the fuel/air
mixture to ignite, which causes a drop in engine
speed and a significant increase in CO-content.
Observe the safety precautions listed on the
container.

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

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

Indicated on display
- Press buttons -0-, -0- and -1- to input display group number 1, and
press -Q- button to confirm input.
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24-98

If engine speed drops, or the value displayed for oxygen sensor control changes:
Read Measuring Value Block 1 1 2 3 4

Indicated on display (1-4 = display fields)
- Monitor oxygen sensor control in display field 3.

Display fields

1 2 3 4
Display group 1: Idle test
Display xxxx RPM
xxx.x C
xx.x% xxxxxx
Indicates Engine speed
(in 40 RPM
steps) Engine
temperature Oxygen sensor control Adjustment
conditions
Range 0-6800 RPM --- -25.0 to 25.0 % ---
Specified
value 760-960 RPM --- In the range of -10.0 to 10.0% the value must
fluctuate by at least 2% ---
- Systematically spray parts of intake air system with engine leak detector spray.
- Check for leaks in area of intake air system most recently sprayed, and eliminate leaks.
Pa
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