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2008 gmc envoy_sle
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OKay, 2008 Envoy 4.2 eng. 50 k on Envoy I had the check light come on 2 weeks ago days after having to replace the battery, I sure it had no bearing, who knows. It stayed on and had it check at local auto parts store. the code stated that there were a couple of things to check. relays and possible blocked hoses. Wow thanks there only a hundred of hoses to check. We went to the box located in the eng. compartment behind the battery and inspected several relay fuses #64 and a couple of others, they all appeared to be in working order ( none burnt) then inspected several hoses and didn't know what to look for at all or where to start. My friend an I then disconnected the battery for several minutes to reset. Great no more check eng light. Then yesterday started vehicle and bam light is on again. Can someone guide me to where or what else to check, really don't want to take it to dealer and have them tell me it's 500.00 for some simple over sight. Thanks to all
::crazy:
 

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2003 chevy trailblazer_ls
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5,269 Posts
we cant help without a code.
What you describe is all but useless in helping you.
I may as well tell you youre low on blinker fluid.

 

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2003 chevy trailblazer_lt_ext
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968 Posts
I've found that my TB is about the flakiest vehicle I've owned when it comes to CELs. My TB gets more false positives than anything real. I've been told by two dealers to do the following if I can't get it diagnosed right away (like being on a road trip).

1) Is the light solid (not flashing)?
2) Does it run smooth and feel like it has it normal power?
If the answer to both of these is "Yes", then disconnect the battery for ten minutes. Most, not all, codes can be reset this way. If the light CEL goes out, then monitor to see if it comes back on. If so, as is usually the case with my TB, then there the CEL had a false positive, nothing to worry about. If it does come back on (and sometimes it may not for a few days, or even a week or two) and the answer to 1 & 2 is still yes, then its nothing serious and can be driven for quite a while. Its just very annoying, and if you live in a state like WI and have to have it inspected for emissions, you'll fail. Get the codes read, and try to track down the problem.

If the light is flashing though, or if its running poorly, something's going on that needs attention ASAP. Don't wait to get it fixed, or at least don't drive it.

Some will disagree with my approach, but disconnecting the battery doesn't cost anything and can avoid a lot unneeded troubleshooting.
 

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2004 chevy trailblazer_ls
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Some will disagree with my approach, but disconnecting the battery doesn't cost anything and can avoid a lot unneeded troubleshooting.
Yes, but doing so is like painting over a rust spot without properly sanding and filling the area... sure it looks fine for now... but that red stuff is eating the metal under that paint.... :duh:
 

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2003 chevy trailblazer_lt_ext
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Yes, but doing so is like painting over a rust spot without properly sanding and filling the area... sure it looks fine for now... but that red stuff is eating the metal under that paint.... :duh:
I understand what you're thinking, but I don't think your analogy works here. If you could site an example of how "hiding" a code would be "eating" away at something important, that might help me. If there truly is an issue, the code WILL come back. That's the point of my post, and more importantly, that's how the system is designed. Being that I support computer systems for a living, I'm very familiar with all the little glitches that occur for no apparent reason. All it takes to set off a false positive CEL is for the engine to ingest an unusually high amount of C02 or other chemical. Well of course the engine can't properly burn that, then the O2 sensors have a fit and set off a code. To demonstrate, get some SeaFoam or other engine cleaner and spray it in throttle body. It will almost always set off the CEL. But of course you know that there is nothing really wrong, it was caused by the chemicals.

A couple of years ago I towed my trailer through Montana on I90. There were a lot of forest fires burning and we drove through some areas that were pretty smokey, almost like driving through light fog. Anyway, I got a CEL light shortly after driving through the area. I reset it when I got to Yellowstone. On the way back home, I got a CEL again, shortly after driving through the smokey area. Reset it in Wall, SD, and it never came back. That was almost 50k miles ago. If I hid something, it certainly hasn't manifested itself in any way.

Did I mention that two different dealers told me to try this procedure also? Oh, BTW, they were in two different state about 1500 miles apart, so I don't think they are blowing smoke.
 
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