Golf III L4-1984cc 2.0L SOHC (1993)
Knock Sensor: Testing and Inspection
*** UPDATED BY TSB # 289003 DATED OCT. 31, 1990 ***
Knock Sensor
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Start and warm the engine to operating temperature.
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Connect a suitable timing light to cyl #1.
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While watching the timing marks, lightly tap on the cylinder block with a hammer or wrench, near the sensor.
^
The timing should retard at least
3° in conjunction with the tapping.
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If the timing does not change:
a. Check that the knock sensor mounting bolt torque is within specification (engine cold,
15 - 18 ft. lbs.). CAREFULLY, loosen and retorque as
necessary.
WARNING: Disconnect the battery ground strap. Limited space between the alternator electrical connection and the knock sensor
mounting bolt may cause an accidental short between the two components.
b. The harness should be checked for continuity and proper routing.
c. Verify that the terminals for the knock sensor harness connectors are of the same material. Replacement knock sensors have gold plated
terminals. Earlier original equipment sensors have alloy plated terminals. If a knock sensor with gold terminals is installed, be sure to replace
the matching harness connector with gold terminals.
OSCILLOSC0PE TEST
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With the engine "OFF", disconnect the knock sensor harness connector.
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Connect the positive lead of an oscilloscope to terminal 1 and the negative lead to terminal 2 of the knock sensor. Refer to scope manufacture
instructions.
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Start the engine and warm to operating temperature.
Oscilloscope Display
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Operate the engine at
5000 rpm and observe the scope pattern.
^
The oscilloscope pattern should be similar to the example.
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If the pattern does not appear similar to the example, replace the knock sensor.
