With Manufacturer's Scan Tool
Knock Sensor, Checking
NOTE:
- It is extremely important to keep to the tightening torque of 20 Nm to make sure the knock sensors perform perfectly.
- Knock sensor (KS) 1 -G61- and Knock sensor (KS) 2 -G66- have a direct 2-pin connection and therefore have no 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 and dirt
Special tools and equipment
- Test box VAG1598/31
- Multimeter Fluke 83 or equivalent
- Adapter set VAG1594
- Wiring diagram
Check conditions
- On Board Diagnostic must have recognized a malfunction on one or both knock sensors.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes
- Engine speed must be at least 2650 RPM, see display group 28, display field 1
- Engine load musts be at least 40.0%, see display group 28, display zone 2
- Coolant temperature must be at least 80°C, see display group 28, display zone 2.
Test sequence
- Connect scan tool VAG 1551 ((VAG 1552). Start engine and select "Address word" 01 of engine control module. Engine must be running at idling speed. [1][2]Reading and Clearing Diagnostic Trouble Codes
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press keys 0 and 8 for the function "Read measuring value block" and confirm entry with Q key.
Indicated on display:
Read measuring 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 measuring value block 28 ->
1 2 3 4
NOTE: The knock sensor test must be performed during a road test since knock sensor diagnostic is only active at engine speeds above 2650 RPM with an engine load of more than 40%.
- Test drive vehicle with a 2nd person to observe display.
Observe the valid safety precautions when performing a test drive.
- Check specification for knock control in display zone 4.
Specification: Syst. OK
If the specification is 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 specification is not obtained:
Checking resistances and wiring
- Separate 2-pin connector to Knock sensor (KS) 1 -G61- -1- and/or 2- pin connector to Knock sensor (KS) 2 -G66- -2-.
- Measure resistance between the contacts 1+2 at connections to knock sensors.
Specification: Infinity Ohms
If the specification is not obtained:
- Replace knock sensor(s)
- Check DTC memory, if necessary, repair any faults and then erase DTC memory.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes
If the specification is obtained:
- Remove wiper arms and cowl panel.
- Connect test box VAG1598/31 to control module wiring harness. The engine control module remains disconnected.
- Check wiring for open circuit between test box and 2-pin connectors using wiring diagram.
-G61-: -G66-:
Contact 1+socket 106 107
Contact 2+socket 99 99
Wire resistance: max. 1.5 Ohms
- Additionally check wires for short to one another.
Specification: Infinity Ohms
If no fault is detected in the pipes:
- Loosen knock sensor and tighten again to 20 Nm.
- Test drive vehicle again.
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
Enrichment
Full throttle
Overrun
must be attained several times.
- At wide open throttle the speed must exceed 3500 RPM.
- Again check the 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.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes