QuestionI have a 2001 GMC Yukon, I just got it back from the shop(tune-up,100K) and they advised replacing my knock sensor and wire. You said you can test the sensor, how? And where is it?
AnswerHi
Why are they suggesting the replacement of a Knock sensor?
Is the Check Engine light on?
If the check engine light is NOT on, there is NO reason I can think of to replace the sensor.
If it is on, I know the GenII engines (1999-2002) had a problem with water getting into the knock sensor mounting holes, and creating codes due to short circuits (Code P0332) for the REAR sensor ONLY. If you have a code P0327
that is for the front sensor ONLY. No need to replace them both. If you happen to have a code P0325, this code means that someone, somewhwers replaced the PCM (computer) and did not swap the Knoch Sensor Module into the new PCM computer.
Testing...Remove the intake manifold sight shield.
Disconnect the knock sensor jumper harness connector located on the left side of the intake manifold.
Set the DMM to the 400K ohm scale.
Measure the resistance of the appropriate knock sensor using the DMM connected to battery ground.
Is the resistance of the knock sensor between 93 and 107k ohms.
If so the sensors are good
If not Connect the DMM between the appropriate knock sensor signal circuit on the sensor side and the engine block.
Set the DMM to the AC voltage scale.
Important: Do not tap on plastic engine components.
Tap on the engine block near the appropriate knock sensor while observing the signal indicated on the DMM.
Is any signal indicated on the DMM while tapping on the engine block near the knock sensor?
If so check all wires to PCM.
If not replace sensor(s) for the code set.
I hope this helps.
JUST advice from experience.
Good Luck
Pawl
