checking AUDI A4 2000 B5 / 1.G ATW Engine Ignition System Workshop Manual

28-1


Ignition system, checking

General notes on ignition system


Note:

The battery should only be disconnected and
reconnected when the ignition is turned off,
since otherwise the Engine Control Module
(ECM) can be damaged.
For the electric components to work properly, a
voltage of at least 12.7 V is required.
It is possible that the control module will
recognize a malfunction and store a DTC during
some tests. After completing all tests and
repairs, DTC memory should therefore be
checked and erased if necessary.
If the engine only starts briefly and then turns
off again after troubleshooting, repair or
checking of the components, it may be that the
immobilizer is blocking the Engine Control
Module (ECM). DTC memory must then be
checked and if necessary, control module must
be adapted.
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28-4


Ignition coils with power output stages,
checking

Special tools and equipment

VAG1526A
VAG1527B
VAG1594A
VAG1598/31
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28-7


If LED does not light up:
Electrical Wiring Diagrams, Troubleshooting & Component Locations
If LED lights up:
Checking voltage supply
Test requirement:
Electrical Wiring Diagrams, Troubleshooting & Component Locations - Connect VAG1527B voltage tester as follows:Harness connector
Terminal
Measure to
2 B+
4 B+

LED must light up.
- Check wire connections.
- Check voltage supply
Fuses for engine electronics OK
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28-10

- Perform following tests marked with dots:

Checking activation of power output stages
Note:
Fuel must not be injected during the test to avoid damaging catalytic
converter. Connectors must therefore be disconnected from fuel injectors.
Check wire connection from 3-socket relay carrier, position 2, terminal
6 to harness connector at ignition coil terminal 1. Check motronic Engine Control Module (ECM) power supply relay -
J271- Page 28
-13
.
- Remove all harness connectors to injectors.
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28-13


Motronic Engine Control Module (ECM)
power supply relay -J271-, checking

Special tools and equipment

VAG1526A
VAG1594A
VAG1598/31
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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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28-21


Intake Air Temperature (IAT) sensor -G42-,
checking

Special tools and equipment

VAG1526A
VAG1594A
VAG1598/31
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3A
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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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28-26


Engine speed (RPM) sensor -G28-,
checking

Special tools and equipment

VAG1526A
VAG1594A
VAG1598/31
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