Knock sensors, checking

WARNING: This page is about a different car, the 2006 Audi A4, 2005 Audi A4, 2004 Audi A4, 2003 Audi A4, and 2002 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Identifying Special Tools - Knock Sensors, Checking

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Special tools and workshop equipment required

V.A.G 1526 A Multimeter
V.A.G 1594 A Connector test kit
V.A.G 1598/31 Test box

Component location → Component locations, overview

NOTE:

The Knock sensors -G61- and -G66- cannot be tested electrically by themselves..
Use only gold-plated terminals when repairing the cable connectors for the knock sensors.
To ensure that the knock sensors function properly it is important to keep exactly to the specified tightening torque of 20 Nm.
Check connector between knock sensor and wiring harness for corrosion.

Checking knock sensor wiring

Fig 2: Identifying Connectors For Oxygen Sensor

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Disconnect Knock sensor 1 -G61- connector -Pos. 1- or Knock sensor 2 -G66- connector -Pos. 4-.

NOTE:

Fig 3: Removing Coolant Expansion Tank Bolt

Courtesy of VOLKSWAGEN UNITED STATES, INC.

To gain access to the connector, remove coolant expansion tank bolt (arrow) and move expansion tank to the side. Fuel hoses remain connected.

Fig 4: 3-Pin Connector & Terminals

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Test for short between all three terminals in knock sensor connector (terminals 1+2, 1+3, 2+3).

Specified value: ∞ Ω (no continuity) wiring must not be connected to each other.

If there is a connection between terminals, install a new knock sensor.

If no malfunction is found:

Checking wiring from knock sensors to ECM

Connect test box V.A.G 1598/31 to wiring harness for ECM; do not connect ECM. Refer to Electrical testing using VAG1598/31 test box .
Check for open circuit, short to ground, or short to positive in following wiring connections:

Fig 5: Identifying 3-Pin Connector Terminals 1 & 3

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Knock sensor 1 -G61- (cylinders 1 and 2)

Connector Terminal	Test box V.A.G 1598/31 Socket
1 (signal)	106
2 (ground)	99
3 (screening)	108

Fig 6: Identifying 3-Pin Connector Terminals 1 & 3

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Knock sensor 2 -G66- (cylinders 3 and 4)

Connector Terminal	Test box V.A.G 1598/31 Socket
1 (signal)	107
2 (ground)	99
3 (screening)	108

Repair any open/short circuit as necessary.