start AUDI A3 1999 8L / 1.G ATW Engine Ignition System Workshop Manual

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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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Safety precautions

To reduce the risk of personal injury and/or
damage to the fuel injection and ignition system,
always observe the following:

Do not touch or disconnect ignition wires when
engine is running or turning at starting RPM.
Always switch ignition off before disconnecting
or reconnecting wires for the injection and
ignition system, including high voltage wiring
and test leads.
If engine is to be cranked at starting RPM
without starting (e.g. for compression testing),
disconnect connector from ignition coils and
from fuel injectors.
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. Readiness
code must be generated after DTC memory is
erased Page 01
-73
.

Always switch ignition off before cleaning
engine.
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- Disconnect 4-pin harness connector -1- at ignition coil -2-.

If specified values are not obtained: - Connect VAG1527B voltage tester to connector terminals 2 and 3.
- Operate starter briefly.

LED must blink (brief blink signal).
- Connect VAG1598/31 test box at wiring harness to Engine Control
Module (ECM), do not connect ECM Page 24
-19
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28-27
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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Component location Overview of component
locations Page 24
-5
The Camshaft Position (CMP) sensor provides
the ignition position for cylinder 1.
For failure, knock control is switched off and the
ignition angle is retarded slightly since a cylinder
allocation is no longer possible. In addition, the
boost pressure of the turbocharger is decreased.
Engine will continue to run without Camshaft
Position (CMP) sensor signal and can also be
restarted:

When a malfunction is recognized, the Engine
Control Module (ECM) initiates one ignition
spark per cylinder for each crankshaft rotation.
The offset of one engine rotation will have no
noticeable effect on the injection. Instead of
occurring with intake valves open, injection will
be "pre-loaded" (in front of closed intake valve).
This has only a minor effect on the quality of the
mixture preparation.
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Checking activation

- If installed, slide back rubber grommet on
connector for Camshaft Position (CMP) sensor,
but leave connector connected.

Note:
Connector socket numbers are shown on the rear side of the connector.
Note:
Voltage testers do not go out completely during low current pick-up
between activations by the ECM, but rather continue to glow a little and
then get significantly brighter during activation. - Connect VAG1527B voltage tester between sockets 2 (CMP sensor
signal) and 1 (B+).
- Operate starter for a few seconds.

LED must blink.
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Checking Ground (GND) wire

If all specified values are being reached and the LED does not blink
(measured between terminal 1 and 2 with starter and connector
connected):
If specified values are not obtained:
Checking wire connections between Camshaft Position (CMP)
sensor and Engine Control Module (ECM) - Check following wire connection for open circuit and short circuit to B+:Harness connector
Terminal
Measure to
3 B+
- Repair open circuit or short circuit if necessary.
- Replace Camshaft Position (CMP) sensor.
- Connect VAG1598/31 test box at wiring harness to Engine Control
Module (ECM), do not connect ECM Page 24
-19
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