96 tahoe service engine soon light

[jstil]

I recently aquired a 1996 Tahoe LS 4wd 5.7L automatic with 147K miles
Took the tahoe to local service center for the service engine soon light, and was told that there were no codes and that the VCM was bad, gararge replaced the VCM and all was good for 3 days. Then the light was back on. I checked the usual, gas cap, any hoses unhooked under the hood. took the tahoe back and the gararge could not find any codes and sent the VCM back to the company for reprogramming. All was good for a couple of weeks. the dreaded light came on again. checked under the hood and found a breather hose from the valve cover unhooked from the air intake tube. (just had the tahoe in for a wheel alignment) perhaps the tech knocked the hose loose. anyway the light went out after a couple of days. fast forward 2 more weeks, the light comes on again. checked most areas again and found nothing amiss. light went out again after the 2nd day. another week and a half and the light is on again. this purchase seems to be a lemon, I love the tahoe, but this is driving me NUTS! do I have to spend many $$$$ to get this straightened out. I have read the auto parts store has a free scanner to use, but will it diagnose the light that will show no codes?
thanks

[snobear3n8]

Originally Posted by jstil

I recently aquired a 1996 Tahoe LS 4wd 5.7L automatic with 147K miles
Took the tahoe to local service center for the service engine soon light, and was told that there were no codes and that the VCM was bad, gararge replaced the VCM and all was good for 3 days. Then the light was back on. I checked the usual, gas cap, any hoses unhooked under the hood. took the tahoe back and the gararge could not find any codes and sent the VCM back to the company for reprogramming. All was good for a couple of weeks. the dreaded light came on again. checked under the hood and found a breather hose from the valve cover unhooked from the air intake tube. (just had the tahoe in for a wheel alignment) perhaps the tech knocked the hose loose. anyway the light went out after a couple of days. fast forward 2 more weeks, the light comes on again. checked most areas again and found nothing amiss. light went out again after the 2nd day. another week and a half and the light is on again. this purchase seems to be a lemon, I love the tahoe, but this is driving me NUTS! do I have to spend many $$$$ to get this straightened out. I have read the auto parts store has a free scanner to use, but will it diagnose the light that will show no codes?
thanks

Had the same problems with my 96 tahoe awhile back. Turned out to be the Catylatic Converter. No more problems after I replaced it!

[MT-2500]

If the light is on there should be a code in the computer. But it may not be a present or hard code. It could be a intermedent code. But the could or should be stored in the computer memery as a history code.
You may need a good engine/trans capable scanner to read all codes in history and present.
Yes some auto parts places give free code checks.
But Use Caution when getting the free code checks please.
Some parts places do offer free code checks. And also free repair advice. But beware. Just get the code no and post it back here and someone will help you.
They offer the free code checks in the hope of increasing there parts sales.
Almost all of them will also offer mechanical advice and some know what they are doing.
But just remember most of them are parts people pulling codes for free.
Not trained professional tech/mechanics. Even if they pull a 02-sensor code or another sensor related code it does always mean to replace that sensor and your problem will be fixed.
Please just get the code no and post it back here and someone will help you.

MT-2500

[jstil]

Originally Posted by MT-2500

If the light is on there should be a code in the computer. But it may not be a present or hard code. It could be a intermedent code. But the could or should be stored in the computer memery as a history code.
You may need a good engine/trans capable scanner to read all codes in history and present.
Yes some auto parts places give free code checks.
But Use Caution when getting the free code checks please.
Some parts places do offer free code checks. And also free repair advice. But beware. Just get the code no and post it back here and someone will help you.
They offer the free code checks in the hope of increasing there parts sales.
Almost all of them will also offer mechanical advice and some know what they are doing.
But just remember most of them are parts people pulling codes for free.
Not trained professional tech/mechanics. Even if they pull a 02-sensor code or another sensor related code it does always mean to replace that sensor and your problem will be fixed.
Please just get the code no and post it back here and someone will help you.

MT-2500

yesterday on my way home from work the light went out, I took the tahoe to autozone and asked if they could put the scanner on anyway to retrieve any stored codes in history and the counter person said that if the light was not on, there was nothing he could do so back to square one. Is there some kind of driving practice that I am doing that is causing this? I was cautioned not to drive with both feet as this will cause the vcm to think the tranny is slipping. thanks for the replies.

[MT-2500]

Quote
Took the tahoe to local service center for the service engine soon light, and was told that there were no codes and that the VCM was bad, gararge replaced the VCM and all was good for 3 days. Then the light was back on.

If the light is or has been on it has a hard code or major problem.
A flashing light may indicate a engine miss.
Have you returned to the local service center and asked them to recheck it. If they replace the pcm they should at least recheck it free of charge to help find the problem. The pcm should be under warranty ask them to check and see if you may have a bad one.
When light comes back on get it checked while light is still on. Run it by parts house and leave it running and have them check it or Find a good repair shop that can read out history codes with a good scanner.
Also I would check the tune up end of it plugs and fuel filter and air filter.
Good luck and if you can get the code no post it back.
MT-2500

[GMMerlin]

Originally Posted by jstil

yesterday on my way home from work the light went out, I took the tahoe to autozone and asked if they could put the scanner on anyway to retrieve any stored codes in history and the counter person said that if the light was not on, there was nothing he could do so back to square one. Is there some kind of driving practice that I am doing that is causing this? I was cautioned not to drive with both feet as this will cause the vcm to think the tranny is slipping. thanks for the replies.

If the PCM turned on the light, there is a code stored...one thing about autozone..these guys sell parts, they cannot diagnose anything.
It's like going to McDonalds and asking for a Whopper
Tell the guy to check the codes, if he says he can't do it, call his bluff and tell him to do it any way. Write down the code and post it here.

Your vehicle is not a lemon! (mainly because it doesn't fall under the definition of a lemon)
What you are suffering from is a mechanic that doesn't know how to properly diagnose and repair your vehicle.

[jstil]

Originally Posted by MT-2500

Quote
Took the tahoe to local service center for the service engine soon light, and was told that there were no codes and that the VCM was bad, gararge replaced the VCM and all was good for 3 days. Then the light was back on.

If the light is or has been on it has a hard code or major problem.
A flashing light may indicate a engine miss.
Have you returned to the local service center and asked them to recheck it. If they replace the pcm they should at least recheck it free of charge to help find the problem. The pcm should be under warranty ask them to check and see if you may have a bad one.
When light comes back on get it checked while light is still on. Run it by parts house and leave it running and have them check it or Find a good repair shop that can read out history codes with a good scanner.
Also I would check the tune up end of it plugs and fuel filter and air filter.
Good luck and if you can get the code no post it back.
MT-2500

Thanks for the reply, I bought a small scanner 3030 Innovia and read the codes myself. And this little wonder will read the stored codes even if the light is not on. So much for Autozone's line of &*#$%
Also it will erase the codes with a push of a button.
The codes revealed were:P1406,P1870
I looked them up and P1406 is EGR valve pintle position circut. After reasearch I found that it could be carbon buildup in the EGR valve. Have to investigate.
P1870 is Trans component slipping. I believe I set this code by driving with both feet to place the tahoe up on drive on ramp so that I could change the oil and filter and the transmission works fine.
I erased the codes and the scan tool told me that the EGR driving cycle would be needed to test the egr system. Been 4 days and no light, but I won't go crazy this time, I have satisfaction knowing that this little tool will point me in the right direction (possibly).

[MT-2500]

Watch for codes to come back.
The codes doe not seet just by driving onto a ramp.
Code 1870 is trans code if it comes back you have a problem in that area.
Good Luck
MT