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

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.

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.

After that, I'd swear off their brake parts forever.

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:

WTF does the condition of the backing plate have to do with a wheel cylinder shearing off? This had better be good.

Doc

Oh hell yeah. I did just that as soon as I saw it. I wish I had of snapped some pics of it but I was so pissed off I just threw it in a ziploc bag, threw it away and drank beer. This happened in my garage thank god, could have been bad news on some of the crazy Appalachian roads I drive on daily.

I have NEVER used AZ parts on front ends, drivetrains, etc. I used to use their brake parts (calipers, wheel cylinders, hardware, etc.) until this happened. Until just recently I used their electronic components and have had good results with them; I'll give em' that. I've even switched back to Delco oil filters from Mobil 1 so I don't have to make a trip to AZ when it's maintenance time.

Doc

Hi!

Hey! I take offense to that! :-)

Well, no, wait, I guess I can't. Mine is great except for the radio. But that was soon fixed.

William The Guesser (and S-10 Owner)

I'm gunna side with you William. I really enjoy zipping around in my wife's

98' Sonoma. Fast as hell, decent size bed, quiet inside. Yeah, it'll never go offroad (2WD, SLS Sport package, sits pretty low to the ground), but on-road it serves it's purpose. I personally like the bigger cab of the FS trucks as I tend to spread out when I'm driving, but for a small truck, it's damn comfy on long trips.

Haven't had any problems with it. Needed brakes and a waterpump but that's it so far. And yeah, the radio was the first thing I did to it. Dumped a Sony ES head unit in her, Blaupunkt speakers in the dash and doors and a JL Audio sub in the back (wife likes her country music thumpy!).

Doc

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

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.

Same here, NO electronic parts at AZ Bought a coil for my '89 S blazer, it was arcing through the side, AZ coil started doing the same after about 1k miles. Needless to say the NAPA coil is still going strong as I sold the truck to my brother 2yr ago. One good thing about AZ is that when they came to town the local NAPA adjusted their prices down to compete, a win for me as I couldn't get a price break before.

How useful would that have been? If your such a great engineer, do the math. It's been pointed out that there were probably 25 different configurations for the S10 alone in that one model year. Your 64k prom probably wouldn't have even covered them. You'd still have to widen the address bus, and those two changes alone would have been significant enough to raise the price of the vehicle. Economics is just as important as calculus to a good engineer. If your product isn't price competitive, it doesn't sell. BTW, a meg of RAM was well over a 100 bucks back then. EPROM wouldn't have been cheap, especially when it wasn't economic to buy it in blocks much larger than 4k back then. Nobody used 64K EPROMS in 85. So you'd need to use an array of them. Ever seen one of those old video cards from the 80's, the ones over a foot long to hold all the memory array?

And your best guess as to how many different combinations of code GM currently offers?

Nope. Look up the concept of yield, think about economics, and think also about the reliability issue. Dedicated designs are inherently more reliable then multiple path systems.

Why would you think that? And don't forget the international market in your rebuttal.

So GM would still need many, and so would Ford, Chrysler, etc. And there'd be different ones for each model year. It still wouldn't be economical for AZ to stock them, given the low demand. As has been pointed out, these parts RARELY go bad and can just be swapped to a new computer if someone hasn't SCREWED with it.

You need to get more sleep.

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

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

Not true, the 27C64 was in wide use in 1985. Here is a link to some design papers on Intel's site:

You might want to look at some date codes on some 64K and larger EPROMS as you will see that they were in use earlier than that. Oh, the EPROM was invented in the early 70s. And in 1977, while only 512B and 1KB, were in wide use. So, by the early mid-80s, reasonably sized EPROMS were cheaply available.

Rita

My books say the 27C64 is 8K, as does page 12 of that link

80C31BH + CHMOS EPROM The 27C64 and 87C64 are Intel's 8K byte CHMOS EPROMs.

Enough EPROM to do the entire GM lineup would have been expensive and consume a lot of board space. I use 1985 as the time frame, but I have no idea when the design was originally conceived. Probably started in the very early 80's, making the problem even more dramatic. I started college in 82 in EE, digital electronics emphasis, so this stuff is pretty familiar to me. The 8088 was the most widespread processor in use

1. You also have to remember the 12 bit address bus on the ECM. That would have been expensive to redesign. Cool link, btw. Brought back memories.

BTW, I have an old RS ad from 1989 for a Tandy 5000. 20 MHZ 386 with 2 Megs of RAM, 3.5 floppy, no HD, monitor or mouse. A mere $8499. I can Email the add, as I have it on a jpg.