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E C M Reflash ????

Big T

Big T

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Location
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I am facing an issue with my C A s m o g c h e c k in that their "new" equipment will not connect or talk with the OBD II E C M in my '99 K2500 Suburban (sorry about spacing, as I hope it makes it search proof). I have a Heath tune and I am wondering whether anything done in the tune (ie no recognition of vac operated wastegate) might be causing this communication problem? Would I have to go back to a stock tune? Last time the State BAR said that my vehicle did not need the OBD IIA check, only MIL codes. However, they have since change the laws and apparently the software. No talkie to their computer and no Passy the test.
 
Last I heard the problem lies with the fact that there machine checks the checksums in the ECM, and modified ECM's will not report what the machine is looking for, hence it doesn't like what it sees and gives an error.
 
THEFERMANATOR said:
Last I heard the problem lies with the fact that there machine checks the checksums in the ECM, and modified ECM's will not report what the machine is looking for, hence it doesn't like what it sees and gives an error.
Click to expand...

So it sounds like I need a stock OBD II E C M ?
 
Alright, looks like I'm going to buy a used stock OBD II ECM. Plenty available on car-part.com. Are there years to avoid? Do I need an ECM from a '99? Will an ECM from a '96 work? Does it matter if it's from a 3500 truck?
 
1999 is year & option specific especially if you have a NP246 it has 3 speed sensors, there is a difference in 6.5td engine series also make sure its not an ecm from a manual trans vehicle. If running a bigger turbo that will be an issue that your map will see and defuel as over boost.
 
It has an auto transmission. All the stock equipment goes back on for the s m o g c h e c k. Thus need for stock ECM.

What's a NP246?

So are you saying I need an ECM from a '99 K2500 Suburban 4wd?
 
FellowTraveler said:
If running a bigger turbo that will be an issue that your map will see and defuel as over boost.
Click to expand...

Not sure this is a factor as this is one is only necessary for a few miles, and then goes back on the shelf for a couple years.


Big T said:
What's a NP246?
Click to expand...

The transfer case model / number.


Big T said:
So are you saying I need an ECM from a '99 K2500 Suburban 4wd?
Click to expand...

IIRC, part number wise, it is the same part number from 96 - 02 that uses a 6.5 and had not read of any differences in the guts (core processor, memory, etc).

For absolutely playing it safe (no codes, no idiot lights), have either a dealership or reputable shop flash it with the correct 99 code. I stating that, have a strong hunch that it is going to look for the vacuum system and code if it is not seeing the vacuum working normally . . .
 
Get one from a 99 auto, and make sure it is from a 2500/3500 so the shift points won't be way off. The 3 speed sensors used on the np246 had 2 speed sensors going directly to the tccm, and the output/vss still went to the vssb where it sends out the same speed signal to the ecm, abs, radio, and also a signal to the tccm. The ecm could care less. The 96 ecm is different in that it doesn't use vats, so you need a 97+ to keep the security light off.
 
JayTheCPA said:
Not sure this is a factor as this is one is only necessary for a few miles, and then goes back on the shelf for a couple years.




The transfer case model / number.




IIRC, part number wise, it is the same part number from 96 - 02 that uses a 6.5 and had not read of any differences in the guts (core processor, memory, etc).

For absolutely playing it safe (no codes, no idiot lights), have either a dealership or reputable shop flash it with the correct 99 code. I stating that, have a strong hunch that it is going to look for the vacuum system and code if it is not seeing the vacuum working normally . . .
Click to expand...

Will the transfer case model be listed on the door label? It's got the push button transfer case, if that means anything.

Vacuum is now working properly. Took about a mile hard on the pedal to get the turbo to spool. Wastegate actuator works. Just a matter of the solenoid working after sleeping for 2 years.

There's tons of ECM's listed, but very few for '99. The ones listed for '99 are for C2500 trucks.

How much would a dealer charge to re flash it? If I had to go that route, might as well buy the cheapest one available for like $60.

Yes this will be used for a couple miles, every two years. And yes, I will get the KOJO tune.
 
Whenever I've had mine reflashed, I've always had to give the VIN number as well. Not to add more drama to the issues at hand but, the VIN isn't coded into the ECM is it?
 
Paveltolz said:
Whenever I've had mine reflashed, I've always had to give the VIN number as well. Not to add more drama to the issues at hand but, the VIN isn't coded into the ECM is it?
Click to expand...

Inquiring minds want to know. If this is talking to the State BAR computers, I want to know if it's telling it the VIN# and all the goodies that go with that. Not good if it's sending info that it's a C3500 dually and they're staring at a K2500 Suburban.
 
Big T, I got your email and will make the requested call Monday morning...reminder on the 'smarter-than-me' phone.
Merry Christmas to you and yours and, of course, the TTS gang.
Happy Holidays Amigos,
Pavel
 
THEFERMANATOR said:
Get one from a 99 auto, and make sure it is from a 2500/3500 so the shift points won't be way off. The 3 speed sensors used on the np246 had 2 speed sensors going directly to the tccm, and the output/vss still went to the vssb where it sends out the same speed signal to the ecm, abs, radio, and also a signal to the tccm. The ecm could care less. The 96 ecm is different in that it doesn't use vats, so you need a 97+ to keep the security light off.
Click to expand...
Well, my bad again I stand corrected on the 246 comment , sorry.....another thing that may come back and bite you would be an exhaust w/o soot trap if there is none.
 
Last edited:
FellowTraveler said:
Well, my bad again I stand corrected on the 246 comment , sorry.....another thing that may come back and bite you would be an exhaust w/o soot trap if there is none.
Click to expand...

Catalytic converter, errrrrr soot trap, is covered from last go around on S M O G C H E C K. It's in place. They also made me fab 3" exhaust from the downpipe to the soot trap. This is all part of my biennial crash kit. I put everything in a plastic tub and store. This time notes and a stock ECM are going in the tub.

All you bastards enjoying the warm weather can thank me and my Global Warming soot belching 6.5.
 
The ECM normally has the vin programmed into it for obd2, but scanners normally cannot read the vin out of ecm's prior to 2000 as there was a protocol change in 2000 regarding vin readout.
 
Found a 6.5 ECM from a 1999 Suburban K2500 with Automatic (see attached). Assuming I get this, will I need to reflash for VIN# at the dealer? Does it need to be in the truck to do that? What does that cost? Or can I just install and try to get it passed as is?
 

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