Isolating the Computer, ESC, and Distrib Module (continued)

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They reman the computer since the chips very seldom fail. AND there are places to get new chips. GM will sell you all you could ever want. So will Rock Auto Online they have them from 25.79 for the CALPAK and up to
64.79 for the EPROM depending on what you need takes 3 days since they don't stock them either. (those will work in the 1228062 ECC) Oh and just to be helpful you are probably looking for either 1228544 or 16060380 EPROMs That depends on the emissions option your vehicle has, And assumes it isn't a CA or Canadian vehicle originally.
BUT because they are application specific most places don't carry them. Think about this, Take just your truck as an example. There are at least 25 different EPROMS for JUST the S series with a 2.8 in 1988. Auto/man trans, CPI/TBI, 4x4/2x4, Gear ratios, w/AC wo/AC and what which computer and state/country the vehicle you have all require different programming depending on options. Now you being a big "engineer" you should realize things like this.
Of course it really sounds more like you have no clue how a ECC unit works since you claim the chips should work "No, I used the 'old' chips. The sockets matched. There was 1 big, 1 small." Really sounds like a pro there... I really like the idea of just shorting out sensors to cure things, never gave a thought to the fact that some of them might just burn out circuitry when you short them did you. Oh and last I knew AZ doesn't accept returns on electrical items.
--
Steve Williams


"Elliott" < snipped-for-privacy@comcast.net> wrote in message
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Steve,
I'm not ignorant of what you suggest below (ie: blowing parts by shorting or even missmatching them, etc). However, w/ less than 3 days to go before loading the rental truck, I took my chances - and for that I can run it, even drive it (though not ready for inspection). Thanks for the source info, I will archive it and possibly buy from there if Gary's doesn't work.
NG (another + for AZ), AZ took back the computer and gave back my original/core. AND I was truthful with them about why I was returning it - So I could have the core part back since it at least runs and because I didn't have a ready source for chips. That's one of the things I like about AZ - they're customer friendly (past dealings with GM dealers have been less so and far more expensive).
When I get an address again I can mail order stuff, or maybe I will find good service at a GM dealer where I'm going - or better maybe Gary's will have something that will work for $25 +10 Core - I'll pay $35 and take a chance at this point. I might even buy 2 of them since I've been doing business there since I was a kid and they know me - maybe even will give me 2 for the price of 1.
Elliott
"Steve W." wrote:

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Odds are he just didn't know any better.

You could start by getting friendly with your local Chevrolet (or GMC) dealerships parts department. Their parts catalogs should list out which PROMs would be possible fits. The PROM is stamped with a 4 letter code, this is called the "broadcast code," once you know which broadcast codes might work, you'll stand a better chance of locating one in a bone yard. FYI, an original untouched ECM will have the broadcast code printed on the outside label, knowing this will save you effort when tramping thru the bone yard.

Actually, it makes perfect sense. The PROM is what tailors the ECM to the individual application. It allows a relatively small number of ECM chassis to fit a broader range of applications. It also allows that running changes be made when problems occur. Chrysler and Ford build their ECMs the way that you say makes more sense, but when a programming change is needed, it comes at a much higher expense to the consumer.

Has GM actually told you that a new PROM is unavailable? Have you hit the proverbial brick wall in attempting to have them assist you in trying to determine which is the correct PROM for that truck?

Swapping the old PROM to the new computer has been standard operating procedure WRT GM ECMs for over 25 years. This predicament of yours occurs most often as the result of ignorance and careless handling, same as when a vehicle is in a front end accident but the repair person(s) don't see fit to replace the original tune up label and vacuum diagrams as a part of the repair. Eventually, someone -needs- that information and learns a hard lesson in frustration.
Now you know why I have such a strong dislike when it comes to sloth, ignorance and carelessness.
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Hi!

Well, there's the junkyard.
Or --presumably-- (meaning to say I see no reason why this couldn't work) you could always extract the ROM from a working donor vehicle and copy it with a good ROM burner attached to a computer. I don't know if you could do the same with the CALPAK (which I believe is the smaller of the two chips) though.

When you've got a truck that didn't come with the right stuff, it's easy to agree. You've gotta get the proper code from somewhere...and that can be irritating and hard.
But otherwise it is somewhat understandable, especially when the computer could be used with more than one vehicle, set of options or microcode revision/type. It would be nice to see a system where you buy the computer and then get the code you need burned to some nice new chips for your vehicle's computer.

Good point. ROM chips don't always last forever. But read on...

...the only problem with that is the fact that GM probably has a copyright on the code that the engine computer runs, and therefore places restrictions or totally forbids its distribution outside of "official channels".
William The Guesser
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A good design would have been (hope GM is smart enough to do this currently - before Japan does)... To use a PROM big enough to hold all of the programs (ie: 100x to replace 100 different chips all in 1). And on the connector have the vehicle provide it's idenity (base address) so that it would run the right program (preferrable to the old "dip switches" - though those could also work). Elliott
"William R. Walsh" wrote:

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So, engineer, care to tell me what memory was costing back in the 80's when this computer first came out?
I believe the EPROM's used were typically 4K (12 bit address bus, which you'd have had to widen for your scheme). 400K back then would have been insane, and really lowered the yield.
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Even back then these parts were cheep enough that a 64K PROM could have been reasonably used. Today, there's no excuse for a design like that. Like I said I hope GM is doing this now - anybody know what's in the 2000+ ECMs? Should be allot less vehicle dependencies. ie: 1 chip 'should' be enough to cover at least all of 1 type vehicle or maybe all of 1 type engine. Elliott PS: It's almost 5 am and I'm leaving for Binghamton (will stop at Garys).
John Alt wrote:

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elliot: gm's pcm's have been programmable since 1995-6. they require a dealer to download the info (vin and all) from the old one, and install it into the new one.
Re: Isolating the Computer, ESC, and Distrib Module (continued) Group: alt.autos.4x4.chevy-trucks Date: Sat, Apr 10, 2004, 4:42am From: snipped-for-privacy@comcast.net (Elliott) Even back then these parts were cheep enough that a 64K PROM could have been reasonably used. Today, there's no excuse for a design like that. Like I said I hope GM is doing this now - anybody know what's in the 2000+ ECMs? Should be allot less vehicle dependencies. ie: 1 chip 'should' be enough to cover at least all of 1 type vehicle or maybe all of 1 type engine. Elliott PS: It's almost 5 am and I'm leaving for Binghamton (will stop at Garys). John Alt wrote:
A good design would have been (hope GM is smart enough to do this currently - before Japan does)... To use a PROM big enough to hold all of the programs (ie: 100x to replace 100 different chips all in 1). And on the connector have the vehicle provide it's idenity (base address) so that it would run the right program (preferrable to the old "dip switches" - though those could also work). So, engineer, care to tell me what memory was costing back in the 80's when this computer first came out? I believe the EPROM's used were typically 4K (12 bit address bus, which you'd have had to widen for your scheme). 400K back then would have been insane, and really lowered the yield.
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yeah, well it is nice, in retrospect (and in light of how cheap memory is today compared to back then) to say 'This is what they shoulda done'
but they didn't, so get on with life

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Actually, the price of memory today had no bearing on what it did back in the 80s when the start of GM's use of the MEMCAL. The standard MEMCAL is a simple EPROM, usually a 27C128 that has 128K of memory space. The binary file that is written to this EPROM is only a small fraction of this 128K space. Keep in mind that any EPROM with 64K, 128K, 256K, 512K, and 1M can be substituted for virtually the same price. These EPROMS are virtually indestructible and are only erasable using an ultraviolet light source for a timed duration. So, GM had the equipment, means, and resources available at the time to do this, but didn't have the desire since it would create too much confusion in the field. It's best to keep the information compartmentalized and group specific.
There is a wealth of great information on burning your own MEMCALs on the web, including BIN images of performance mods for certain vehicles. You will need an EPROM reader/writer and a UV eraser so you can reuse your EPROMs.
Rita
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And Elliot, just go to the local flee market for your burner. I picked up a working one for 50c.
~KJ~

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wrote:

you need to remember economy of scale... if your do it all PROM costs GM just $1 more each... you've just cost them in excess of 10 million dollars. (GM sells about 400,000 new cars a MONTH in north america ALONE).
-Bret

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Yeah, you're not kidding. There were times when I cursed the bastards for not giving me an extra inch of wire in the harness. Come to think of it, that 1" of wire probably cost GM 1/1000th of cent.
Rita
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Rita, Thanks for answering the PROM questions better than I did. NG, 'Good' engineering involves a "design to cost" theoretical approach using typically a 10% rule of thumb for 'extras'. For autos (high volume), the 10% rule of thumb could be reduced to 1%, but less is just bad engineering practice. The 'extras' are typically features that make production and maintinance easier - and thus reduce the Life Cycle Costs. Buit In Test feature are the most common. The PROM size and vehcles covered (prior discussions) are another type that fit the 'extras' category. Most engineers have seen shortcuts that cost and cost and cost. For example, I worked on an prototyped Radar system that was built without any self test features (a managment decision). Every demonstration that was given involved hours of engineering time on the customer's site to debug the basic wiring. Had the 'extra' built in test features been included with the 1st design, those costs would not have occurred again and again. On GM's computers, short wires, inaccessable parts, etc, there have been many service time hours spent - ultimately by the vehicle owners. Even documentation is a factor, and thus here we are spending hours on this NG backengineering problems that aren't described in the owners manual (ok there are proprietary issues to ballance too). "Quality" has become a buzz-word in the industry often construed to be maintinence free operation, but seriously everything gets repaired or replaced sometime for some reason (ie: accident dammage, etc). Thus making things difficult to service is POOR QUALITY. And per an earlier comment, I hope GM does the oversize PROMs with 'all' vehicles by now (before Japan does). Elliott
"Rita Berkowitz" wrote:

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Most OBDII compliant vehicles are set up with EEPROMS already, They are flashed with the correct code to match the vehicles options as one of the last steps before they are shipped out the door of the factory. 99 percent of the devices sold to "Improve" vehicles today (power programmer, Add on boxes) only control the engine/trans at close to WOT. That way they can still say it will not screw up your emissions control equipment. Say you buy a 2000 Dodge Caravan and don't like the way the trans shifts. You can go to a dealer (or a trans shop with the correct tools) and reprogram the controller to give you higher line pressure or different shift RPM levels. Same with a LOT of 1998/9 and up vehicles made in the U.S. The engine code can be altered for more performance (within limits, due to mechanical parts differences) simply by plugging in a computer to the OBD2 port. BUT if YOU alter the code and it causes problems the manufacturer is going to tell you it's your problem. Making things difficult to service depends on what your talking about. I can think of nothing on my wifes 94 S Series that is really difficult to service IF YOU BUY THE PROPER TOOLS. No crescent wrenches and hammers. The only thing I can really say was a bad idea from a service point is one spark plug because it is behind the steering shaft. I bought a compound swivel spark plug socket and solved that problem, and gained a tool that made the rest easier to change as well. As for the computer controls IF you know how to read the codes and troubleshoot intelligently it is a LOT easier than the old days. If you plug in a scanner and don't have a clue you end up spending a lot of time chasing the wrong things.
--
Steve Williams
Near Cooperstown NY
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Steve, Thanks for reminding me of the OBD2 EEPROM usage. Hopefully that approach makes the computers more interchangeable - with some OBD2 service and specialized tools. Elliott
"Steve W." wrote:

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So they charge me $2 extra? Now they have made $10,000,000....
~KJ~

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through in this frickin thread, you're kidding, right?
Remember this next line before hacking up your new computer. Most vehicles have only one "chip" in them, the larger.
If your junkyard computer only has one, it's OK. If it has two, it's OK. I'm not going to bother with splaining the details, just make sure it's from a 2.8 with an automatic. If they don't have one, order a PROM. If AZ doesn't have it, try somewhere else. I don't have access to my books till next week sometime, but I'm not sure that 8062 will work.
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John, No, I used the 'old' chips. The sockets matched. There was 1 big, 1 small. When I got the truck the computer was installed under the dash with only the little chip in there. The big chip was in a bag under the seat. When I put the 2nd chip into the old computer it came allot closer to working than this one does (with those chips) - so obviously they must have both been from the other computer, and not from the truck. And yea frustration is high. At this point I'm thinking I need to go back to AZ tonight and retrieve my old computer ($50 core charge) tonight - and I may as well return this computer. At least that way I can run the truck onto the tow-dolly for moving. I can't even keep it running with this computer (maybe it would try better w/o the chip, but I'm over it w/o even a link for a chip - only a warrantee warning - they can @#$%^&. A J-yard w/ a computer will have both computer and chips. I can keep my old one, and meanwhile if I score a correct set of chips, I know AZ can sell me a brainless computer. Elliott
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Well I'm back from the 650 miles of the Binghamton trip. Gave my daughter an Easter basket too.
I HAVE A NEW COMPUTER and IT WORKS!!!!!!!!!!!! It's a 1228062 from a 91 S-10 Blazer that had a 2.8L with Automatic, 4x4, A/C, and everything looked the same except the MAP sensor was mounted to the TBI rather than to the Air-Cleaner-Assembly. John, I would have gone for the 1227429 if I could have found one - I didn't. I believe the 1228062 is compatible only because I got it chips and all (the link you provided shows they use different base addresses for the PROMs - that's internal to the computers).
So finally it's running w/o the CES light on. Stopping it and reading for codes I only get the acceptable 12!!!. Running with the jumper it does go into the debug mode (flasshing according to rich/lean 02). Remaining bugs are that the idle is inconsistant RPM and the check gages light is on. The idle is probably from leaky vac lines (easy to fix - but hasn't yet been prioritized - will be soon). I believe the check gages light is either for the oil pressure or water temp gages (both of these could use new sending units).
I stopped at Harry's U Pull it in Hazelton on the way up, and found the 91 Blazer with the computer, a fan shroud, and some Vac hoses (all for the price of $2 admission + $22 for the parts). I thought of Doc cause I saw a guy there pulling a wagon (convenient). I asked on my way out if they had a yard-man and they said no (that was the only drawback - they did have a nice collection of vehicles). And I was reminded of the lacking value of my Truck on the way out where they had several vehicles for sale including a late 80's Blazer 4x4 for $1200.
Later, at Gary's I got a dust-cover for the torque converter (though the S-10 had a 4.3 - so I may need to modify to it if it doesn't fit perfectly). That cost a whole $7 + $10 for the yard man to cut the front Y pipe out of the way. They had other blazers and S-10s so had I had more time I may have found it all there too. The big advantage of Gary's was the yard-man. They had 2 of them there Saturday - driving modified Ice Cream trucks for their yard-vehicles. Plug: see www.garysupullit.com.
Elliott
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