AUDI A8 1999 D2 / 1.G AEB Engine Motronic MFI And Ignition System

24-68
If wiring is OK:

- Check ECT sensor resistance across terminal 1 (signal) and terminal 3
(ground).
- Check measured resistance value for appropriate temperature range
using graph below (N24-0157).

Range A: 0 to 50 C

Range B: 50 to 100 C

Examples:
If resistance is NOT OK:
At 30 C, ECT sensor resistance should be 1500-2000 At 80 C, ECT sensor resistance should be 275-375
- Replace Engine Coolant Temperature (ECT) sensor -G62-.
- 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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24-69

Intake Air Temperature (IAT) sensor,
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 diagram
Chilling spray (commercially available)
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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.
Read Measurin
g Value Block
HELP
Input displa
y 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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24-71

- Compare displayed value with specified value
for intake air temperature (display field 4):

Display fields

1 2 3 4
Display group 4: Engine basic settings
Display xxx RPM xx.xxx V
xxx.x C
xxx.x C
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 ---
approx. ambient temperature
1)

--- --- --- Continuation Page 24
-72
, Evaluation of
display group 4
1) If temperature displayed deviates significantly from ambient temperature, check sensor wiring for contact resistance or
open circuit.
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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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Specified value: max. 1.5
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24-73

- Check wiring for short circuit between ECM/test
box and 2-pin harness connector according to
wiring diagram.


Connector terminal 1 to vehicle Ground

Connector terminal 1 to ECM/test box
socket 67

Connector terminal 1 to terminal 2

Connector terminal 2 to vehicle Ground

Specified value:

- Check wiring between ECM and 2-pin harness
connector for short circuit to battery B+.


Connector terminal 1 to vehicle Ground

Connector terminal 2 to vehicle Ground

Specified value: 0 volts

- Check resistance across terminals of IAT sensor -G42-.
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If resistance is NOT OK:
Specified value: approx. 1.6-2.8 k- Replace intake air temperature sensor -G42-.
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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
.
Pa
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) and i
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p://127.0.0.1:8080/audi/servlet/Dis
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yp
e=re
pair&id=AUDI.B5.FU02.24.1

24-75

Engine Speed (RPM) sensor, checking


Required special tools and test equipment

VAG 1598/22 test box
Multimeter US 1119 (Fluke 83 or equivalent)
VW 1594 connector test kit
Wiring diagram

Checking

- Disconnect 3-pin harness connector from engine
speed sensor Page 24
-1 , Component
locations

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

- Check wiring for open circuit between ECM/test box and 3-pin harness
connector.

Connector terminal 1 to ECM/test box socket 56
Connector terminal 2 to ECM/test box socket 63
Connector terminal 3 to ECM/test box socket 2
Pa
ge 100 of 135 Motronic Multi
port Fuel In
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(MFI
) and i
gnition s
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11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1