1999 AUDI TT check engine

28-42
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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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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If LED does not blink:

Checking voltage supply

- Disconnect connector at Camshaft Position
(CMP) sensor.

Checking signal wire - Connect multimeter for voltage measurement as follows:Harness connector
Terminal
Measure to
1 Engine Ground (GND)
- Switch ignition on.

Specification: about 5 V
- Connect multimeter for voltage measurement as follows:
Harness connector
Terminal
Measure to
2 Engine Ground (GND)
- Switch ignition on.

Specification: approx. battery voltage
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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
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.
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If, after erasing the DTC memory for a test, a DTC relating to the
Camshaft Position (CMP) sensor (hall sensor) is indicated again, even
though all previous tests were OK, the following malfunction is possible:
Repair Manual, 1.8 Liter 4
-Cyl. 5V Turbo Engine Mechanical, Engine
Code(s): AEB, ATW, Repair Group 15; Valvetrain, servicing
- Check following wire connections for open circuit and short circuit to
Ground (GND) and B+:
Harness connector
Terminal
VAG1598/31 test box
Socket
1 (B+) 98
2 (signal) 86
3 (Ground -GND-) 108
- Repair open circuit or short circuit if necessary.

Shutter wheel for Camshaft Position (CMP) sensor is not aligned
properly.
- Unscrew Camshaft Position (CMP) sensor and check whether shutter
wheel is mounted properly at camshaft (if mounted improperly, locking
lug will get squished when mounting bolt is tightened).
- If position of shutter wheel is OK, check allocation of
crankshaft/camshaft.
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Misfire recognition, checking


Special tools and equipment

Test sequence
VAS5051 with VAG5051/1
orVAG1551 with VAG1551/3A
- 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 displa
y group number XXX

When indicated on display
- Press buttons -0-, -1- and -4- to select "display group number 014" and
press -Q- button to confirm input.
Read Measuring Value Block 14
1
2
3
4

When indicated on display
- Check misfire recognition.
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Display fields

1 2 3 4
Display group 014: Misfire recognition
Display xxx /min xxx %
xxx
---
Indicated Engine
speed
(RPM) Load
Number of ignition misfires
Misfire recognition
Functional
range

activated
locked
Specified
value xxxx/min 15 to
33 % 0
activated
Note
If the specified value is exceeded:
Check combustion misfires of
individual cylinders Page 28
-53


If ignition misfires are to be expected due to
operation conditions (e.g. warm-up,
deceleration shut-down), misfire recognition
is deactivated
If specified value is obtained:

-
Press button.Rapid data transfer
HELP
Select function XX

Indicated on display (function selection):
If specified value is not obtained:
- Press -C- button.
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