Volkswagen Workshop Service and Repair Manuals

Notes:

• ◆ It is extremely important to keep to the tightening torque of 20 Nm to ensure the knock sensors perform perfectly.
• ◆ Only gold-plated contacts may be used when servicing the knock sensor connector contacts.

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required

• ◆ Test box V.A.G 1598/22
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Adapter set V.A.G 1594
• ◆ Current flow diagram

Test conditions

• ● Knock sensor fault recognised by self-diagnosis , interrogating and erasing fault memory.

Checking function

• ‒ Connect fault reader V.A.G 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control unit. When doing this the engine must be running at idling speed.
  (Connecting fault reader and selecting engine control unit .)

• ‒ Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

• ‒ Press keys 0, 2 and 2 for the "Display group number 22" and confirm entry with Q key.

Note:

Checking the knock sensor must be performed during a test drive because the diagnosis of the knock sensor is first activated above an engine speed of 3000 rpm and an engine load greater than 3 ms.

Observe the valid safety precautions when carrying out a test drive => Page 28-6 .

• ‒ Perform a test drive and check knock control specifications on display (display zones 3 and 4)

•      Specification (cylinders 1 and 2): 0...15 °CA

• ‒ Change to display group 23 as follows:
• ‒ Press key 3 (V.A.G 1551) or key ↑(V.A.G 1552).

• ‒ Check knock control specifications on display (display zones 3 and 4)

•      Specification (cylinders 3 and 4): 0...15 °CA

If the specifications are obtained:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the "End output" function and confirm input with the Q key.
• ‒ Switch off ignition.

If the specifications are not attained:

Checking resistances and wiring

• ‒ → Separate blue 3-pin connector to knock sensor 1 (G61).
• ‒ Measure resistance between the contacts 1+2, 1+3 and 2+3 at connections to knock sensors.
       Specification ∞ω

• ‒ → Connect test box V.A.G 1598/22 to control unit wiring harness.
• ‒ Check wiring between test box and 3 pin connector for open circuit using current flow diagram.
       Contact 1+socket 68
       Contact 2+socket 67
       Contact 3+socket 67
       Wire resistance: Max. 1.5 ω
• ‒ Additionally check wires at socket 67 for short to socket 68.
       Specification: ∞ω

If no fault is detected in the wiring:

• ‒ Loosen knock sensor and tighten again to 20 Nm.
• ‒ Carry out test drive.

• During the road test the following operating conditions must be fulfilled:
• ‒ The coolant temperature must exceed 80 °C .
• ‒ When the temperature is reached, the operating conditions
       Idling
       Part throttle
       Full throttle
       Overrun
  must be attained several times.
• ‒ At full throttle the speed must exceed 3500 rpm.

• ‒ Again interrogate the control unit fault memory.

If the fault is still present:

• ‒ Replace knock sensor (G61)