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| Pat | 1992 Convertible, LT1, 6spd, ECM Schematic available? | ||
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Guru Newb
 
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Greetings,
I recently had the "Sys" flashing on the dash resulting in no start. After figuring out My ECM was not communicating with the CCM I replaced my ECM and all is fine. I would like to try and repair my old ECM but need to find a schematic. Anyone have one for the 1992-93 years? Pat 1992 Convertible, LT1, 6spd, 160k miles |
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Posted on: 2007/10/3 3:04
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| bogus | RE:1992 Convertible, LT1, 6spd, ECM Schematic available? | ||
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Grand Imperial Pooh-Bah
 
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whew... good luck...
To the best of my knowledge, the schematic is not available. My other concern is that if you replace components that are not to spec, the new part simply wouldn't hold up. As an aside, the component that has more than likely died is the UART that controls communications. |
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Posted on: 2007/10/3 4:45
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| toptechx6 | RE:1992 Convertible, LT1, 6spd, ECM Schematic available? | ||
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Senior Guru
 
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I agree with Andy, I've never heard of an available schematic. You might want to check with some of the Corvette specialty stores such as Mid America, I think they will rebuild them if you want a spare.
Where did you get the replacement out of curiosity, I understand 92 and 93 ECM's are hard to find? |
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Posted on: 2007/10/3 7:39
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| CasetheCorvetteman | RE:1992 Convertible, LT1, 6spd, ECM Schematic available? | ||
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Elite Guru
 
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Swap the whole thing over to a far superior 94 spec PCM and CCM.
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Posted on: 2007/10/3 8:20
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| toptechx6 | RE:1992 Convertible, LT1, 6spd, ECM Schematic available? | ||
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Senior Guru
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Quote:
Swap the whole thing over to a far superior 94 spec PCM and CCM. Okay mate, explain how that will work considering 94's are MAF and the 92 is speed density? You will need a MAF sensor plus the different duct work, how about the cluster, will it work with the 94 CCM? 94's also fire injectors sequentially so you will need an engine harness to make it work. Sounds like it could get complicated pretty quickly. |
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Posted on: 2007/10/3 10:35
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| CasetheCorvetteman | RE:1992 Convertible, LT1, 6spd, ECM Schematic available? | ||
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Elite Guru
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It was a joke, but since you ask, 94-96 are also speed density, the MAF is for steady state correction. The MAP still controls main fueling in the same of very simular way as a 92/93 with the MAP Vs RPM setup on the VE table. TPS has almost no say whatso ever in fuel control, and WOT is enabled when a certain TPS% is reached for a given RPM (and that is the only part the TPS plays in fuel control). You dont need a MAF on a 94-96, it can be turned off. Yes you will need the harness to do it for the sequential injection, which cuts back to batch fire at a preset TPS% (12.9% factory default) Yes, the cluster will work fine with the CCM.
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Posted on: 2007/10/3 12:16
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| toptechx6 | RE:1992 Convertible, LT1, 6spd, ECM Schematic available? | ||
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Senior Guru
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You lost me completely when you say MAF is for steady state correction. I understand that a MAF car will run without the MAF sensor since the system still uses a MAP sensor to take the baro reading and it is a simple matter to include the speed density fuel tables as a back up system. You do lose the advantage of directly reading the amount of air entering the engine and better control that MAF provides however. You haven't adopted the KOPBET89 philosophy of engine management have you?
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Posted on: 2007/10/3 15:59
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| Pat | Re: Schematic | ||
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Guru Newb
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Thanks for the replies. It sounds like I am not going to find the ECM schematic. I am a electronic technician by trade and really wanted to fix the ECM myself.
I have the ECM out of the case and will try to trace back to the UART. Also will look for any cold solder joints that someone else pointed out. I was lucky to have a 1993 engine and auto trans setup in my garage waiting for a future hot rod conversion. Used the 1993 ECM and traded Proms with my 1992 6spd and have been running ever since. |
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Posted on: 2007/10/3 19:11
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| CasetheCorvetteman | RE:1992 Convertible, LT1, 6spd, ECM Schematic available? | ||
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Elite Guru
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Quote:
You lost me completely when you say MAF is for steady state correction. I understand that a MAF car will run without the MAF sensor since the system still uses a MAP sensor to take the baro reading and it is a simple matter to include the speed density fuel tables as a back up system. You do lose the advantage of directly reading the amount of air entering the engine and better control that MAF provides however. You haven't adopted the KOPBET89 philosophy of engine management have you? It doesnt work that way on a 94 and up. The MAP Vs RPM is what decides fuel. MAF only provides a correction factor. |
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Posted on: 2007/10/3 20:19
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| bogus | Re: Schematic | ||
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Grand Imperial Pooh-Bah
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Quote:
Thanks for the replies. It sounds like I am not going to find the ECM schematic. I am a electronic technician by trade and really wanted to fix the ECM myself. yea... it really does suck, but manufacturers like to keep this stuff secret. |
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Posted on: 2007/10/4 2:50
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| toptechx6 | RE:1992 Convertible, LT1, 6spd, ECM Schematic available? | ||
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Senior Guru
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It doesnt work that way on a 94 and up. The MAP Vs RPM is what decides fuel. MAF only provides a correction factor.[/quote]
How did you determine that mate? Every fuel injection book I've seen on Corvette says 94 through 96 except LT5 are mass air flow systems, not speed density. If the MAF sensor provides the correction factor what are the O2 sensors doing? |
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Posted on: 2007/10/4 8:15
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| CasetheCorvetteman | RE:1992 Convertible, LT1, 6spd, ECM Schematic available? | ||
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Elite Guru
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Well, through many many hours of data logging, many changes and tested changes to PCM calibration with TunerCat, i managed to see a trend (or set one
 ). When i made a quite large change to the VE tables (which control fueling using the MAP and engine RPM) i left the MAF tables completely untouched, so theoretically speaking, the BLM figures for the cells in the VE table i changed shouldnt have been exactly the same, cause the MAF was still saying the exact same amount of air was flowing as before, BUT it didnt work that way, cause instead of my idle BLM figures being down around 110 to pegged at 108, they were now up to 117-114. The only thing i changed on that setup was the VE tables, and Datamaster was still saying almost identical air flow. The MAF does have a say in fueling control, but the big boss is still the MAP. The O2s also both apply correction within a limit. |
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Posted on: 2007/10/4 9:05
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| toptechx6 | RE:1992 Convertible, LT1, 6spd, ECM Schematic available? | ||
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Senior Guru
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Quote:
Well, through many many hours of data logging, many changes and tested changes to PCM calibration with TunerCat, i managed to see a trend (or set one I'm not convinced.  |
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Posted on: 2007/10/5 11:18
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| CasetheCorvetteman | RE:1992 Convertible, LT1, 6spd, ECM Schematic available? | ||
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Elite Guru
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Ill show you when youre here mate.
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Posted on: 2007/10/5 11:45
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