Knock Sensor and Knock Sensor Control, Checking

Required special tools and test equipment
- VAG1551/1552 Scan Tool (ST) with VAG1551/3 adapter cable
- VAG1598/22 test box
- Multimeter US1119 (Fluke 83 or equivalent)
- VW1594 connector test kit
- Wiring diagrams

Checking
- Connect VAG1551/1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (with engine running at idle) Testing and Inspection

Indicated on display

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

Read Measuring Value Block HELP
Input display group number XXX

- Press buttons corresponding to following display group numbers and press -Q- button to confirm input.
- 022: Display group 22, for cylinders 1 and 2
- 023: Display group 23, for cylinders 3 and 4
- 024: Display group 24, for cylinders 5 and 6

Indicated on display (1-4 = display groups)

Read Measuring Value Block 22 ->
1 2 3 4

NOTE: The test must be carried out during a road test because the knock sensor system is only active with engine speed greater than 2600 RPM and engine load greater than 3 ms.

- Road test and compare display with specified values for knock sensor system in display field 1-4.

WARNING! A second technician is required to operate the VAG1551 scan tool during the road test. Service Precautions

Display Group 22:

If displayed values are OK:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Check readiness code.
If Diagnostic Trouble Code (DTC) memory has been erased, or ECM has been disconnected, generate new readiness. See On Board Diagnostic (OBD). Testing and Inspection

Evaluation of Display Groups 22, 23, 24:

Continuation
- Disconnect 3-pin connector from Knock Sensor (KS) 1 -G61-.

- Connect multimeter US1119 (Fluke 83 or equivalent) to measure resistance between connector terminals, using adapters from VW1594 connector test kit.
- Connector terminals 1 and 2
- Connector terminals 1 and 3
- Connector terminals 2 and 3
- Specified value: Infinity ohms

If resistance is OK (no continuity):
- Connect VAG1598/22 test box to Motronic ECM harness connector. Testing and Inspection

- Check wiring for open circuit between ECM/test box and 3-pin harness connector, according to wiring diagram.
- Connector terminal 1 to ECM/test box socket 68
- Connector terminal 2 to ECM/test box socket 67
- Connector terminal 3 to ECM/test box socket 67
- Specified value: max. 1.5 ohms

- Check wiring for short circuits between terminals of 3-pin connector, and between connector and ECM/test box.
- Connector terminal 2 to ECM/test box socket 68
- Connector terminal 3 to ECM/test box socket 68
- Specified value: Infinity ohms

If the wiring is OK:
- Loosen knock sensor and tighten to 20 Nm (15 ft lb).

If the malfunction still exists (stored in DTC memory):
- Replace Knock Sensor (KS) 1 -G61-.
- Check readiness code.
If Diagnostic Trouble Code (DTC) memory has been erased, or ECM has been disconnected, generate new readiness code. See On Board Diagnostic (OBD). Testing and Inspection

- Disconnect 3-pin connector from Knock Sensor (KS) 2 -G66-.

- Check wiring for open circuit between ECM/test box and 3-pin harness connector, according to wiring diagram.
- Connector terminal 1 to ECM/test box socket 60
- Connector terminal 2 to ECM/test box socket 67
- Connector terminal 3 to ECM/test box socket 67
- Specified value: max. 1.5 ohms

- Check wiring for short circuits between terminals of 3-pin connector, and between connector and ECM/test box.
- Connector terminal 2 to ECM/test box socket 60
- Connector terminal 3 to ECM/test box socket 60
- Specified value: Infinity ohms

If the wiring is OK:
- Loosen knock sensor and tighten to 20 Nm (15 ft lb).

If the malfunction still exists (stored in DTC memory):
- Replace Knock Sensor (KS) 2 -G66-.
- Check readiness code.
If Diagnostic Trouble Code (DTC) memory has been erased, or ECM has been disconnected, generate new readiness code. See On Board Diagnostic (OBD). Testing and Inspection