Knock Sensor, Checking
NOTE:
- It is extremely important to keep to the tightening torque of 20 Nm to ensure the knock sensors perform perfectly.
- Knock sensors 1 (G61) and 2 (G66) have a direct 2-pin connector and consequently no contact for the shielding in the connector.
- Only gold-plated contacts may be used when servicing the knock sensor connector contacts.
- Contact surfaces between knock sensor and cylinder block must be free of corrosion, dirt and grease.
Special tools and equipment
- VAG 1598/31 test box
- VAG1526 hand multimeter or VAG1715 multimeter
- VAG1594 adapter set
- Wiring diagram
Test conditions
- On Board Diagnostic (OBD) must have recognized a malfunction on one or both knock sensors, Checking and Erasing DTC Memory.Refer to "Displaying and Reading Trouble Codes/With Manufacture Scan Tool/Check DTC Memory (Function 02)" Testing and Inspection
- Coolant temperature must be at least 85 °C, See display group 28, display zone 3.
Checking function
- Connect VAG1551 scan tool (VAG1552). Start engine and select "Address word" 01 of engine control module. When doing this the engine must be running at idling speed. (Connecting scan tool and selecting engine control module). Refer to "VAG1551 Scan Tool Tools and Equipment
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.
Indicated on display:
Read measured value block
Input display group number XXX
- Press keys 0, 2 and 8 for the "Display group number 28" and confirm entry with Q key.
Indicated on display: (1 to 4 = Display zones)
Read measured value block 28 ->
1 2 3 4
NOTE: Checking the knock sensors must be performed during a test drive because the diagnosis of the knock sensors is not activated until the engine speed exceeds 1800 rpm and the engine is loaded by more than 40%.
- Perform a test drive and check knock control specifications on display (display zone 4)
Observe the valid safety precautions when carrying out a test drive Service Precautions
Display Group 28:
If the specification is attained:
- Press -> key.
- Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
- Switch ignition off.
Continuation:
If the specifications are not obtained:
- Press -> key.
- Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
- Switch ignition off.
Checking resistance of knock sensors
Knock sensor 1 (G61):
- Disconnect 2-pin harness connector to knock Sensor (KS) 1 -G61- (item no.1) and/or the 2-pin harness connector to knock Sensor (KS) 2 -G66- (item no.2).
- Measure resistance between the contacts 1+2 at the connections to knock sensors.
Specification: infinity Ohm
If the specification is not obtained:
- Replace knock sensor(s)
- Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory, Checking and Erasing DTC Memory. Refer to "Displaying and Reading Trouble Codes/With Manufacture Scan Tool/Check DTC Memory (Function 02)" Testing and Inspection
- Read readiness code. If DTC memory has been erased or engine control module was disconnected from permanent positive, readiness code must be generated again: Refer to "Monitors, Trips and/or Drive Cycle/ Reading Readiness Code" Testing and Inspection
Engine code AWW. Refer to "Monitors, Trips and/or Drive Cycle/Generating Readiness Code" Testing and Inspection
Engine code AWP. Refer to "Monitors, Trips and/or Drive Cycle/Generating Readiness Code" Testing and Inspection
If the specification is obtained:
- Check wiring.
Checking wiring
- Connect VAG1598/31 test box to control module wiring harness. The engine control module remains disconnected.
- Check wiring between test box and 2-pin connector for open circuit according to wiring diagram.
G61: G66:
Terminal 1+Socket 106 107
Terminal 2+Socket 99 99
Wire resistance: max. 1.5 Ohm
- Additionally check wires for short to one another.
Specification: infinity Ohm
If no wiring fault is detected:
- Loosen knock sensor and tighten again to 20 Nm.
- Perform a test drive again and check knock control specifications on display.
Observe the valid safety precautions when carrying out a road test. Technician Safety Information
During the road test the following operating conditions must be fulfilled:
- The coolant temperature must exceed 85 °C
- When the temperature is reached, the operating conditions
Idling
Part throttle
Wide open throttle
Overrun
must be attained several times.
- At wide open throttle the engine speed must exceed 3500 rpm.
- Again check control module DTC memory.
If the malfunction is still present:
- Replace knock sensor(s)
- Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory, Checking and Erasing DTC Memory. Refer to "Displaying and Reading Trouble Codes/With Manufacture Scan Tool/Check DTC Memory (Function 02)" Testing and Inspection
- Read readiness code. If DTC memory has been erased or engine control module was disconnected from permanent positive, readiness code must be generated again: Refer to "Monitors, Trips and/or Drive Cycle/ Reading Readiness Code" Testing and Inspection
Engine code AWW. Refer to "Monitors, Trips and/or Drive Cycle/Generating Readiness Code" Testing and Inspection
Engine code AWP. Refer to "Monitors, Trips and/or Drive Cycle/Generating Readiness Code" Testing and Inspection