AUDI TT 1999 8N / 1.G ATW Engine Ignition System Service Manual

- Check wire connections.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
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- Connect multimeter for voltage measurement as
follows:

VAG1598/31 test box
Socket
Measure to
121
1)

Engine Ground (GND)

1) The motronic Engine Control Module (ECM)
power supply relay -J271- continues to direct
current to terminal 121 of the Engine Control
Module (ECM) for up to 15 minutes after ignition
is switched off.

- Switch ignition on.


Specification: approx. battery voltage
If specified value is not obtained:

- Check wire connections.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

-
Check motronic Engine Control Module (ECM)
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power supply relay -J271- Page 28
-13
.
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Knock recognition control stop,
checking

If a DTC is stored regarding "Knock control
regulation limit reached":

- Perform following tests:

Possible cause
Corrective action
DTC for all cylinders

Poor fuel quality
Operating instructions - Change fuel quality
or
Cylinder 1/2 or 3/4
Knock sensor tightened to incorrect torque- Loosen knock sensors and tighten to 20 Nm

Knock sensor faulty- Check knock sensor Page 28
-41


Corrosion at harness connector- Check harness connector

Engine accessories loose- Secure engine accessories
DTC for one Cylinder
Engine damage- Check compression pressure

Engine accessories loose- Secure engine accessories
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Knock sensors, checking

Special tools and equipment

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

Note:

Knock Sensor (KS) 1 -G61- and Knock Sensor
(KS) 2 -G66- themselves cannot be electrically
tested.
Use only gold-plated terminals when servicing
harness connector for knock sensors.
For the knock sensors to function properly, it is
important that tightening torque be exactly 20
Nm.
Check harness connector from knock sensor to
wiring harness for corrosion.

Checking knock sensor wiring

- Disconnect harness connector for Knock Sensor (KS) 1 -G61- (item no.
5) or Knock Sensor (KS) 2 -G66- (item no. 4) in engine compartment.
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Check wires from knock sensors to Engine Control Module (ECM). - Check all three terminals at knock sensor connector for short circuit to
each other (terminal 1+2, 1+3, 2+3).

Specification: (no continuity) - the wires must not have any
connection to each other
- If there is no connection , replace knock sensor.
- If no short circuit is detected, check knock sensor wires:
- Connect VAG1598/31 test box at wiring harness to Engine Control
Module (ECM), do not connect ECM Page 24
-19
.
- Check following wire connections for open circuit and short circuit to
Ground (GND) and B+:

Knock Sensor (KS) 1 -G61- (cylinder 1/2)
Harness connector
Terminal
VAG1598/31 test box
Socket
1 (signal) 106
2 (Ground -GND-) 99
3 (shielding) 108
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Knock Sensor (KS) 2 -G66- (cylinder 3/4)
Harness connector
Terminal
VAG1598/31 test box
Socket
1 (signal) 107
2 (Ground -GND-) 99
3 (shielding) 108
- Repair open circuit or short circuit if necessary.
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Camshaft Position (CMP) sensor 2 -G40-,
checking

Special tools and equipment

VAG1526A
VAG1527B
VAG1594A
VAG1598/31
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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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