SES Light for knock sensor - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 General Tech Q&A > General

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  #1  
Old 09-12-2009, 01:26 AM
mypetropig's Avatar
mypetropig mypetropig is offline
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2003 Chevy TrailBlazer LS
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SES Light for knock sensor

why ses light keeps coming on with code for knock sensor when it has already been replaced. 03 TB LS with JET module,K&N drop in filter, airaid trottle body spacer and resonator delete. The light has been off for a few months but recently came back on after pulling a trailor.
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  #2  
Old 09-12-2009, 01:29 AM
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the roadie the roadie is offline
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Maybe it's knocking?

Try Seafoam or some other carbon buildup remover. Or higher octane fuel?
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Old 09-12-2009, 01:40 AM
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mypetropig mypetropig is offline
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2003 Chevy TrailBlazer LS
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knock sensor

Idont hear any kocking and I run 93 octane,while pulling the trailer I averaged about 3000 to 3500 rpm due to a strong head wind.I got the light to go off and stay for a few months after we had to replace the t-stat. Is this a common problem with TrailBlazers...knock sensor that is ? Ive only had the truck for a few months,72k and my mother in law was previous original owner.
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Old 09-12-2009, 02:14 AM
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What's the precise code? I don't seem to remember a lot of complaints about knock sensors at all.
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Old 09-12-2009, 11:14 AM
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mypetropig mypetropig is offline
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knock sensor

I dont recall the exact code,the folks at Auto Zone told me that it was knocksensor bank 1. Does this code appear every time the engine knocks or pings if only for a short while or does it appear only after the cumputer cannot advance or retard the timing to cure the condition because I dont hear any pinging or knocking. I run Z-max in the gas and oil approx every 3 or 4 oil changes. The engine was turning consistantly higher rpm than normal for an extended period of time so I wonder if it was just working some of the carbon build out and a combo of these things and cheap gas...I guess Ill have to wait and see if the code comes back,before the t-stat it came with about every tank and this is the first time in about 4 or 5 months.
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Old 09-12-2009, 11:42 AM
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Need the exact code to give an exact diagnosis.

One guess might be at high RPM that you're getting a rattle that's setting off the sensor, and then the computer retards the ignition and power suffers needlessly. One report here was that a deteriorating water pump bearing was setting off the knock sensor! That was unexpected.
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Old 09-12-2009, 11:55 AM
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mypetropig mypetropig is offline
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knock sensor

I had a bad bearing in the water pump and it cause a vibration at hwy speed. But the water pump had been replaced a few weeks ago and even with that going on it did not trip the code. Now it feels smooth at speed, depending on the road of coarse. Power does not seem to suffer best I can tell.
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  #8  
Old 12-05-2009, 11:55 AM
JTJammer JTJammer is offline
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knock sensor

The knock sensor set off the service light. I'm going to clean the throttle body and see if that helps. I did unplug the battery for over an hour and the service engine light did not go off. Any ideas on how to get the light to reset?
Thanks!
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Old 12-05-2009, 01:39 PM
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A scan tool with the "code reset" feature can turn the light off. Also normal driving will do it (usually three drive cycles), depending on the computer's determination of how severe the code is. As long as you have fixed the root cause.

The reason that a mere battery disconnection won't clear most codes is that would otherwise be an easy way to cheat the emissions inspection. If there's a valid code set, they force you to fix the problem and drive around to prove it to the computer before turning off the SES light. Imagine that.
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  #10  
Old 12-05-2009, 02:35 PM
JTJammer JTJammer is offline
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Thanks Roadie.

I just finished cleaning the throttle body. I'll let in run a few days to see if the light turns off.

If the light doesn't turn off, do you think it's the sensor or something else? I just had the fuel tank replaced with the recall. Took me a week to convince the dealer it was a recall item. When driving off of the lot, the engine was running rough. Didn't think much about it since the battery had been disconnected and I knew it needed to reset. After 2 stops on the way home the check engine light goes on. I bring it back to the dealer and the dealer says its the knock sensor and the would like to replace it for $600. I said not thanks and brought the truck home. I think the sensor went off due to the rough ride after the gas tank replacement. Hopefully it'll go off in a couple of days.

Thanks,
JT
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