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SpectatorRacing ECM upgrade - what's necessary
Elite Guru
1685 Posts
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2007/12/28 19:00



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As part of my ongoing investigation into the no-start condition I'm considering upgrading to a '94/95 PCM from my '93 ECM. I like the capability and flash programmability of the newer model.

What exactly does this entail?

I have to program out:

VATS
MAF
Secondary O2's
AIR
EGR

I need to update my wiring harness. I also heard I need to switch to the heated O2 sensors. What else?
Posted on: 2008/5/15 15:55
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BrianCunningham Re: ECM upgrade - what's necessary
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If you could get the complete harness out of a wreck, that would be best.

You'll want to nail down the no start condition 1st.

If it's not starting due to a bad sensor, that same one will be there when you put the new one in.

BTW The fast system ECU ( no experience ) runs with and w/o the opti, distributor or crank trigger, your choice.

http://www.fuelairspark.com/Products/chevy/LT1/over.asp

FAST makes a harness for later model LT1's but it's really for HotRod installations.
http://www.fuelairspark.com/WhatsNew/Files/4504-FASTflyer.pdf
Posted on: 2008/5/16 9:13
Edited by BrianCunningham on 2008/5/16 9:35:27
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Polo Green 95 LT1 6-spd http://mysite.verizon.net/vzevcp74/
383 LT1/Vortech Supercharger/AFR heads/Rod end suspension/Penske-Hardbar dual rate coilovers/Wilwood 6pot brakes
NCCC Governor: http://BayStateCorvetteClub.com
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BillH Re: ECM upgrade - what's necessary
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I think I read somewhere that Painless had this upgrade harness. Might be worth checking their website.
Posted on: 2008/5/16 10:16
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bogus Re: ECM upgrade - what's necessary
Grand Imperial Pooh-Bah
San Pedro, CA
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I would be SHOCKED if painless has an upgrade harness. The last time I checked their site, their Corvette stuff stopped at 1982. Seriously.

I will find a link, I am still waiting on info for one... reminds me, time to drop an email.
Posted on: 2008/5/16 10:41
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SpectatorRacing Re: ECM upgrade - what's necessary
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Quote:

BrianCunningham wrote:
You'll want to nail down the no start condition 1st.

If it's not starting due to a bad sensor, that same one will be there when you put the new one in.

BTW The fast system ECU ( no experience ) runs with and w/o the opti, distributor or crank trigger, your choice.

http://www.fuelairspark.com/Products/chevy/LT1/over.asp

FAST makes a harness for later model LT1's but it's really for HotRod installations.
http://www.fuelairspark.com/WhatsNew/Files/4504-FASTflyer.pdf


The FAST system looks great, but I'm looking at close to $3000 in parts to install it. The ECM alone is $2100. I should be able to upgrade to a 94 PCM for about $400. All I need is the PCM ($100) a reprogram ($150) and an upgraded harness.

I can either update my current harness if it shows no damage for the price of the connectors to the PCM ($40) or I can buy a complete '94 harness for $500 from several sources - Howell engine dev, Painless, etc.

AS for the no start, I agree it's smart to figure out what's wrong before making a modification like this which could introduce new variables, but everything checks out. There is NOTHING wrong with any components or wiring on my friggin' car. There's nowhere else to turn...

My only hope is that when I test the brand new MSD opti on Monday it fails. But I seriously doubt it will, and even if it did I should still see spark at the coil.
Posted on: 2008/5/16 11:41
Edited by SpectatorRacing on 2008/5/16 12:10:00
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BrianCunningham Re: ECM upgrade - what's necessary
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What's it not getting?
spark? fuel? neither?
Posted on: 2008/5/16 12:25
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NCCC Governor: http://BayStateCorvetteClub.com
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SpectatorRacing Re: ECM upgrade - what's necessary
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Quote:

BrianCunningham wrote:
What's it not getting?
spark? fuel? neither?


Enjoy! If you have any ideas I'd be very interested. It's killing me.

http://www.corvette-guru.com/modules/ ... t_id=32818#forumpost32818
Posted on: 2008/5/16 13:15
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BrianCunningham Re: ECM upgrade - what's necessary
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Quote:

SpectatorRacing wrote:
Quote:

BrianCunningham wrote:
What's it not getting?
spark? fuel? neither?


Enjoy! If you have any ideas I'd be very interested. It's killing me.

http://www.corvette-guru.com/modules/ ... t_id=32818#forumpost32818


Quote:

SpectatorRacing wrote:
It has a stock ECM and other components, but this is a race car with a stand alone EFI system, so no interactions wtih VATS, the CCM, etc.


How did you bypass the VATS and the CCM for use as a standalone?

EDIT:
Nevermind, you programmed it out sorry.

If it works on the bench, but not in the car, the problem has to be in what's different.
Posted on: 2008/5/16 13:46
Edited by BrianCunningham on 2008/5/16 14:36:24
_________________
Polo Green 95 LT1 6-spd http://mysite.verizon.net/vzevcp74/
383 LT1/Vortech Supercharger/AFR heads/Rod end suspension/Penske-Hardbar dual rate coilovers/Wilwood 6pot brakes
NCCC Governor: http://BayStateCorvetteClub.com
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bogus Re: ECM upgrade - what's necessary
Grand Imperial Pooh-Bah
San Pedro, CA
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I am looking into a 94 PCM pigtail adaptor from Extreme Motorsports.
Posted on: 2008/5/16 23:50
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CasetheCorvetteman Re: ECM upgrade - what's necessary
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QLD, Australia
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The secondary O2 sensor is on the right bank, if its not there, all it will do is set a DTC, secondary O2 is not for engine management control. It wont even turn on the SES light.

The primary O2s in a 94 are heated yes.

youll also need a different ICM.
Posted on: 2008/5/17 0:20
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SpectatorRacing Re: ECM upgrade - what's necessary
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Quote:

CasetheCorvetteman wrote:
The secondary O2 sensor is on the right bank, if its not there, all it will do is set a DTC, secondary O2 is not for engine management control. It wont even turn on the SES light.

The primary O2s in a 94 are heated yes.


Sweet, so I can just change the two I have and ignore the third?

Quote:
youll also need a different ICM.


Yeah, I saw that they were different part numbers. Thanks, case. Any other sensors different (TPS, coolant temp, IAC, etc?)

Andy - what's this adapter? Might save me some money building a custom harness for the new computer. BTW, found lots of them on eBay for less than $100.
Posted on: 2008/5/17 20:56
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CasetheCorvetteman Re: ECM upgrade - what's necessary
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Youll keep the same IAC, CTS should be a standard item, injector harness will be different due to squential injection, most other things are the same.

You can ignore the right bank secondary O2 sensor yes.
Posted on: 2008/5/17 22:12
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bogus Re: ECM upgrade - what's necessary
Grand Imperial Pooh-Bah
San Pedro, CA
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I am waiting on info for the harness adaptor.

as I learn more, I will share!!!
Posted on: 2008/5/18 0:15
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SpectatorRacing Re: ECM upgrade - what's necessary
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Turns out the ignition module from my car will run a '96. I did some investigation as to why the part numbers were different, but most of the searches i did show them to actually be interchangeable.

Strange. There is a significant price difference, though. I love capitalism.
Posted on: 2008/5/18 19:41
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LD85 Re: ECM upgrade - what's necessary
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Indianapolis, Indiana
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If I am not mistaken you can send your harness to Jim at www.jimsperformance.com and he will re-pin your harness and do a diagnostic on the harness for you. He did mone for an 85 to an 86-89 for $150
Posted on: 2008/5/18 19:46
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SpectatorRacing Re: ECM upgrade - what's necessary
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Quote:

LD85 wrote:
If I am not mistaken you can send your harness to Jim at www.jimsperformance.com and he will re-pin your harness and do a diagnostic on the harness for you. He did mone for an 85 to an 86-89 for $150


That's an excellent contact. Thanks, I'll call him tomorrow!
Posted on: 2008/5/18 19:49
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LD85 Re: ECM upgrade - what's necessary
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Indianapolis, Indiana
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Jim is 1st Class, and he has a 406ci Vette, and he programs Gen-7 and otehr aftermarket EFI systems.

Let us know what he says!
Posted on: 2008/5/19 8:55
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SpectatorRacing Re: ECM upgrade - what's necessary
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Quote:

LD85 wrote:
Jim is 1st Class, and he has a 406ci Vette, and he programs Gen-7 and otehr aftermarket EFI systems.

Let us know what he says!


This guy knows his $h!t. He'll help me get the damn car running and then he'll be building a new harness so I can upgrade to the newer computer.

I can't thank you enough, it's the resource I've been looking for.
Posted on: 2008/5/19 16:55
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LD85 Re: ECM upgrade - what's necessary
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Awesome, Jim is #1 at what he does!
Posted on: 2008/5/19 17:39
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