"service engine soon" light and lifter noise on GMC pickup

I have an '00 GMC Sierra 4.8L with 30k miles. The "Service Engine Soon" light comes on persistently. Mechanic says it's the 'knock sensor.' The
only knock we can hear is a very slight noise from a lifter. Mechanic says it's not worth doing the repair but can't keep the light from coming on. Any suggestions on how I can keep the light off, short of disconnecting it? Some kinda additive to quiet the lifter? Try another sensor? Thanks in advance for any help.
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The knock sensor detects vibrations typically caused by detonation. The knock sensor will not detect lifter noise. The two are independent of each other. If the SES light is on, you should be able to go to any Autozone and have them read the codes stored in the PCM. That should give you a good place to start your diagnosis.
-Bruce
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I agree knock sensor will not sense lifter noise. If it is it is faulty. And the knock sensor coming on should not set the light on.
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Sometimes the connection is bad. If the connection is not bad, replace the sensor. They go all the time. The resistance should run about 5.49 M-Ohm on most cars.
Rick
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. . ===== ===== snipped-for-privacy@hotmail.com (ZenCohen) cried out:
I have an '00 GMC Sierra 4.8L with 30k miles. The "Service Engine Soon" light comes on persistently.
Mechanic says it's the 'knock sensor.'
The only knock we can hear is a very slight noise from a lifter.
Mechanic says it's not worth doing the repair but can't keep the light from coming on. Any suggestions on how I can keep the light off, short of disconnecting it? Some kinda additive to quiet the lifter? Try another sensor? Thanks in advance for any help.
==== ====
here is just one site of hundreds for basic operation info on the sensor...... (google is yer friend) . Address:http://home.flash.net/~rjgeorge/knock.htm
A suggestion........ find yourself another mechanic. Any tech that thinks lifter noise on a 30,000 mile motor is insignificant, and is unable to give you a pinpoint reason for their inability to keep the knocksensor code from returning...... IS AN IDIOT. jest my opinion
A "very slight noise" from a lifter SHOULD NOT set a knocksensor code. But yer idea of slight and mine might not be the same.
You can TRY additives to eliminate the valve train noise, which may or may not eliminate the code from resetting. Dumber things have been initiated to cure worst symptoms, and I've seen things dumped into engines that make you scratch yer head and wonder how in the hell it cured the problem. So my suggestion would be try it if you want to...it's an inexpensive test at worst, and you can always do an oil change to get out whatever it is you dump in it.
I would go to the drug store and get some old fashioned "castor oil" and put in it.... if it's going to work...the noise will stop within jest a few minutes of you putting it in. I've used it several times over the years in cars that smoke bad, or have tapping, after they've sat for a week or so at the shop before being picked up. Sometimes it works......... sometimes you jest have to look the cussingmer in the eyeballs and shrug. :)
If it doesn't work...get yerself another tech to hook up the ole scanner and tap on that engine block to see how sensitive the sensor is. because the tech your using has exhausted his capabilities of performing in a proficient manner. Find one more proficient, or live with the symptom.
let us know ~:~ MarshMonster ~:~
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