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ECM Test

Big T

Big T

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So I plugged in the stock ECM from a 1999 Suburban K2500 4wd 6.5 just to test it. Did the KOKO thing and then went to start it. I'd get a brief catch like a couple cylinders and back to just cranking. Did this many times, no difference. Unplugged it and put my tuned ECM back in and it started right up. Warmed it up, then shut it down and put on the stock ECM. Same thing, catch a little, then just cranking.

Any ideas why the stock ECM would not work? Is it due to the Security thing? Do I need it flashed for my VIN #?

I put back the performance ECM and the ATT and exhaust will go back on tomorrow.
 
You did the 3 sets of key on try to start, wait ten minutes, then turn it off and repeat? Sure sounds like the VATS isn't taking.
 
Big T said:
No I did not. Only did the KOKO, once. I will try again tomorrow.

What is VATS?
Click to expand...
Vehicle anti theft system, AKA passlock. Whenever you swap the 97+ ECM's, you have to do the VATS learn so the ECM will learn the code from the PASSLOCK module. It consists of turning the key on, trying to start it, leave the key on for 10 minutes until the security light goes out, then shut the key off. Do this 3 times, and on the 3rd time it should start up and learn the code from the PASSLOCK module.

From the tech library.
http://www.thetruckstop.us/forum/threads/theft-deterrent-learn-97-year-vehicles.39166/
 
I'm on round 4 of this exercise and it's still the same. The security light does go out after a wait, but when I try to start it, the security light is flashing and I just get a kick out of the engine and then nothing. Trying another round.

Tried another two rounds of attempted start and off for 10 minutes. Never started. Reinstalled performance tune and started immediately.
 
Last edited:
Big T said:
I'm on round 4 of this exercise and it's still the same. The security light does go out after a wait, but when I try to start it, the security light is flashing and I just get a kick out of the engine and then nothing. Trying another round.

Tried another two rounds of attempted start and off for 10 minutes. Never started. Reinstalled performance tune and started immediately.
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You try to start it and leave the key on until the security light goes out, then turn the key off for 30 seconds, then repeat.
 
THEFERMANATOR said:
You try to start it and leave the key on until the security light goes out, then turn the key off for 30 seconds, then repeat.
Click to expand...

Aright, got it to work. On a couple I did not follow the 30 second rule. I guess it was the coffee. It's running now and running great. I will take it for a spin, then unplug and reinstall the performance tune. Then all the stock equipment comes off and ATT goes back on. Thanks!
 
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Drove it on a test drive. It's a cute little truck......as in a dog. Definitely less smoke on the snap test. The performance tune has enough smoke to have some of the testing guys questioning it.

Pulled the stock ECM and reinstalled the performance ECM. Need to let it cool while I run down some flange nuts for the ATT.
 
And got all the performance equipment back on. Took 2 hours to swap turbos. That inside rear nut on the turbo mount is a pita. Took another hour to swap exhausts. Back to normal for another 2 years.
 
and for the lookout for a sweet 1997 so you are exempt from all of this. :) lol

It is 97, correct? or is it 98 that is exempt in CA?
 
GM Guy said:
and for the lookout for a sweet 1997 so you are exempt from all of this. :) lol

It is 97, correct? or is it 98 that is exempt in CA?
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95 is exempt from the electrical testince it isn't obd2, but even they are subject to the snap and opacity tests.
 
Wow! Here it anything from 1968 or newer. Unless it's over 20 years old registered as a classic, meaning minimal miles driven per year.
 
I am glad to live in KS. :) no emissions at all. (maybe in KC or Wichita, but not here)

Big T, would you be open to buying a 97 or older if the price and condition was right? If so, any color preference? I could keep an eye out while trolling craigslist. I assume you want to keep a 95+ for the nicer interior?
 
GM Guy said:
I am glad to live in KS. :) no emissions at all. (maybe in KC or Wichita, but not here)

Big T, would you be open to buying a 97 or older if the price and condition was right? If so, any color preference? I could keep an eye out while trolling craigslist. I assume you want to keep a 95+ for the nicer interior?
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Yes, interested in another, but the condition must be right. Mine came from Illinois via Pennsylvania and Delaware. Had some rust, but I am very leary of rust belt trucks. Would like another Suburban K2500. Dilemma is that I've heard that the early oil squirter blocks were the most prone to cracking. I haven't opened up my 1999 (no reason to), but it was made in May of 1999. So far, it's been great.
 
Big T said:
Yes, interested in another, but the condition must be right. Mine came from Illinois via Pennsylvania and Delaware. Had some rust, but I am very leary of rust belt trucks. Would like another Suburban K2500. Dilemma is that I've heard that the early oil squirter blocks were the most prone to cracking. I haven't opened up my 1999 (no reason to), but it was made in May of 1999. So far, it's been great.
Click to expand...

MAY 99 & newer are the enhanced blocks very stout the squirter size is smaller too.
 
Well if you find a truck with an engine built before 1/97, then it is most likely a pre squirter block. Not all 97's got the revised block.
 
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