engine AUDI A4 1998 B5 / 1.G ATW Engine Ignition System User Guide

28-15


If specified value is not obtained: - Connect multimeter for voltage measurement as follows.Harness connector
Terminal
Measure to
1 Engine Ground (GND)
- Switch ignition on.

Specification: approx. battery voltage
- Switch ignition off.

- Pull off rubber seal of plenum chamber cover in direction of arrow.
- Remove cover -1- toward front.
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If wire connection is OK: - Check following connection for open circuit according to wiring
diagram: 3-socket relay carrier in E-box, plenum
chamber, position 2
Terminal
Harness connector at
ignition coils

Terminal
6 1
- Repair open circuit if necessary.
- Check voltage supply of motronic Engine Control Module (ECM) power
supply relay -J271- Page 28
-18
.
- Check activation of motronic Engine Control Module (ECM) power
supply relay -J271- Page 28
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.
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Checking voltage supply

If specified value is not obtained:
Electrical Wiring Diagrams, Troubleshooting & Component Locations
If no malfunctions are found in wires: - Connect multimeter for voltage measurement as follows.3-socket relay carrier in E-box, plenum
chamber, position 2
Terminal
Measure to

2 Engine Ground
(GND)
9 Engine Ground
(GND)

Specification: approx. battery voltage
- Check wire connection between central electronics and voltage supply
relay for open circuit.
- Replace central electrics.
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Checking activation

If specified value is not obtained: - Connect multimeter for voltage measurement as follows.3-socket relay carrier in E-box, plenum chamber,
position 2
Terminal
Measure
to

4 B+
- Switch ignition on.

Specification: approx. battery voltage
- Switch ignition off.
- Connect VAG1598/31 test box at wiring harness to Engine Control
Module (ECM), do not connect ECM Page 24
-19
.
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If no malfunctions are detected: - Check following wire connection for open circuit and short circuit to
Ground (GND) and B+: Relay carrier below left cover, at bulkhead
Terminal
VAG1598/31 test box
Socket
4 21
- Repair open circuit or short circuit if necessary.
- Replace motronic Engine Control Module (ECM) power supply relay -
J271-.
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28-22
Component location Overview of component
locations Page 24
-5

Test sequence

- Connect VAS5051 tester or VAG1551 scan tool
and select control module for engine electronics
using "address word" 01 Page 01
-10
. Engine
must run at idle.
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.
Read measurin
g value block
Q
Enter display group number XXX

When indicated on display
- Press buttons -0-, -0- and -4- to select "display group number 004" and
press -Q- button to confirm input.
Read Measuring Value Block 4
1
2
3
4

Indicated on display
- Check specified value for Intake Air Temperature (IAT) sensor in
display field 4:
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Display fields

1 2 3 4
Display group 004: Intake Air Temperature (IAT), engine at idle
Display xxxx/min xx.x volts
xxx.x C
xxx.x C
Indicated Engine speed
(RPM) Battery
voltage Coolant
temperature Intake Air Temperature (IAT)
Functional
range
-48.0 to 143.0 C
Specified value xxxx/min 12.0 to 15.0 V
80.0 to 110.0 C
From ambient temperature up to 110
C
1)
1) If a temperature is indicated which differs greatly from ambient temperature of sensor, check sensor and sensor wires for
contact resistances and open circuit.
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Checking wire connections

- Connect VAG1598/31 test box at wiring harness
to Engine Control Module (ECM), do not connect
ECM Page 24
-19
.

- Disconnect connector -1- at Intake Air Temperature (IAT) sensor -G42-
(item no. 2).

- Check following wire connections for open circuit and short circuit to
Ground (GND) and B+: Harness connector
Terminal
VAG1598/31 test box
Socket
1 85
2 108
- Check both wires to each other for short circuit.
- Repair open circuit or short circuit if necessary.
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Engine speed (RPM) sensor -G28-,
checking

Special tools and equipment

VAG1526A
VAG1594A
VAG1598/31
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28-27
Component location Overview of component
locations Page 24
-5

Note:
The engine speed (RPM) sensor detects RPM
and reference marks. The engine cannot be
started without a signal from the engine speed
(RPM) sensor -G28-. If the engine speed (RPM)
sensor -G28- signal fails while the engine is
running, the engine will stop immediately.

Test sequence

- Before performing test, check sensor for proper
installation and proper fitting.

Note:
Coolant reservoir screws must be removed and coolant reservoir must be
placed to side in order to access the harness connector. The coolant
hoses can remain connected. - Disconnect harness connector for engine speed (RPM) sensor -G28-
(item no. 3) in engine compartment.
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