Knock Sensor and Knock Sensor Control, Checking
Knock Sensor And Knock Sensor Control, Checking
NOTE:
- The intake manifold must be removed to remove and install the knock sensors.
- It is extremely important to maintain a tightening torque of 20 Nm (15 ft lb) to ensure that the knock sensors perform adequately.
- Only gold-plated contacts may be used when servicing the knock sensor connector terminals.
Special tools and equipment
- VAG1598/22 test box
- Multimeter US1119 (Fluke 83 or equivalent)
- VW1594 connector test kit
- VAG1527B voltage tester
- Wiring diagrams
Checking conditions
- On Board Diagnostic (OBD) must have recognized a malfunction for one or both knock sensors.
Checking function
- Connect VAG1551/1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (with engine running at idle). Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG1551/VAG1552 Scan Tool" under "Engine" 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!
- When driving or riding in an airbagequipped vehicle, NEVER hold the scan tool or other test equipment in your hands or lap while in motion. Objects between you and the airbag increase the risk of injury in an accident.
- During a test drive in an airbag-equipped vehicle, test equipment must always be fastened to and operated from the rear seat by a second technician.
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.
- Switch ignition off.
- Check readiness code .If Diagnostic Trouble Code (DTC) memory has been erased, or ECM has been disconnected, generate new readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
Evaluation of display groups 22, 23, 24
Continuation:
Resistances and wiring, checking
- Disconnect 3-pin connector from Knock Sensor (KS) 1 -G61- -1- and/or 3-pin connector from Knock Sensor (KS) 2 -G66- -2-.
- Connect multimeter US1119 (Fluke 83 or equivalent) to measure resistance between connector terminals, using adapters from VW1594 connector test kit.
- Knock sensor terminals 1 and 2
- Knock sensor terminals 1 and 3
- Knock sensor terminals 2 and 3
- Specified value: Infinity Ohms
- Connect VAG1598/22 test box to Motronic ECM harness connector.
- Check wiring for open circuit between ECM/test box and 3-pin harness connector using appropriate wiring diagram.
Knock Sensor (KS) 1 -G61-:
- 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
Knock Sensor (KS) 2 -G66-:
- 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 wires at test box socket 67 for short to test box sockets 60 and 68.
- Specified value: Infinity Ohms
If wiring is OK:
- Loosen knock sensor and tighten again to 20 Nm (15 ft lb).
- Road test again and check knock sensor control specifications on display.
WARNING!
- When driving or riding in an airbagequipped vehicle, NEVER hold the scan tool or other test equipment in your hands or lap while in motion. Objects between you and the airbag increase the risk of injury in an accident.
- During a test drive in an airbag-equipped vehicle, test equipment must always be fastened to and operated from the rear seat by a second technician.
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.
- Check DTC memory again.
If DTC is still present:
- Replace knock sensor(s).
- Check readiness code. If Diagnostic Trouble Code (DTC) memory has been erased, or ECM has been disconnected, generate new readiness code. Monitors, Trips, Drive Cycles and Readiness Codes