ECU EPROM bit rot?

[brianl703]

Has anyone encountered problems with the EPROM in the ECU going corrupt with time on vintage vehicles?

I know it happens with vintage (1980s) computers.

Or were vintage ECUs more likely to be using mask-programmed ROMs which wouldn't have this problem?

 

[nthach]

I would think the use of PROMs(the ones with a clear window for UV to wipe the chip) was rare in cars - regular ROM was more likely. EEPROMs didn’t make their way into cars until the 1990s.

Dead capacitors would be more of a concern.

 

[Skippy722]

It’s possible, but like nthach said capacitor failure is more likely. Or solder failure.

 

[eljefino]

Solder failure is big. IDK when they cut down on the lead in solder but they had some growing pains when that happened.

The fuel injection relays in my 1991 volvos both failed the same way, bad solder. Just needed to re-flow it to bring them back.

The GM tuning world played with a standard EEPROM chip for the late 80s vehicles, maybe check in with that scene.

 

[ka9mnx]

I would think it's possible. All solid state read/write devices have finite life limit (similar to solid state computer drives) and the older they are the lower the read/write limits.

 

[Trav]

Solder failure is big. IDK when they cut down on the lead in solder but they had some growing pains when that happened.

The fuel injection relays in my 1991 volvos both failed the same way, bad solder. Just needed to re-flow it to bring them back.

The GM tuning world played with a standard EEPROM chip for the late 80s vehicles, maybe check in with that scene.

With Euro cars its called RoHS, when they started that crap electronics reliability took a big hit. After 02 I believe it is also applicable to domestics too.

 

[CorvairGeek]

I would think the use of PROMs(the ones with a clear window for UV to wipe the chip) was rare in cars - regular ROM was more likely. EEPROMs didn’t make their way into cars until the 1990s.

Dead capacitors would be more of a concern.

GM put them in every North American car gasoline engine computer (CCC) starting in 1981 from a Chevette to a Cadillac V8/6/4.

 

[michaelluscher]

The PROM in my 1983 G body is soldered to the ECM, and does not have a window for UV light to get in

Later CAL-PAK and MEM-CAL systems were different

 

[CorvairGeek]

The PROM in my 1983 G body is soldered to the ECM, and does not have a window for UV light to get in

Later CAL-PAK and MEM-CAL systems were different

I've got MEM-CAL systems too. I may have to go look, I've got ECMs starting 1981. I didn't think I had a senior moment...

 

[michaelluscher]

I've got MEM-CAL systems too. I may have to go look, I've got ECMs starting 1981. I didn't think I had a senior moment...

I think around '85 they went to P4
My experiences are almost exclusively the early feedback carb units
A training video for guidance

 

[LDM]

Has anyone encountered problems with the EPROM in the ECU going corrupt with time on vintage vehicles?

I know it happens with vintage (1980s) computers.

Or were vintage ECUs more likely to be using mask-programmed ROMs which wouldn't have this problem?

Almost never happens on GM ECMs. And yes, they used regular EPROM for most of their OBD1 ECMs all the way through to the mid 90s when the switch to OBD2 occurred in 96. My 95 Tahoe and K3500 truck both had the MEMCAL with EPROMs. I still have a bunch of old EPROMs laying around for tuning these vehicles, don't see much use for them anymore these days as there are cheap EEPROM and FLASH style replacement chips that are quicker and easier to use. 2732A, 27C128, 27C256, and 27C512, they were all used in various years and ECMs but almost all the 27Cxxx are soldering into a MEMCAL unit that also has some other circuitry on them.

Last major project I've done for OBD1 stuff was a few years back after I picked up my 89 Camaro, I converted it from the 1227165 ECM used in 89 with a MAF sensor to the 1227730 ECM used in 90-92 with speed density to allow for better tuning. The older MAF sensors were never very good to begin with and all the remans out there today are pretty much garbage. Got tired of trying to get the idle to not bounce all over the place so I went ahead and got everything I needed and made my own harness adapter, then setup my own tune. Got the car running perfect and it made for a interesting project. Hardly anyone does any OBD1 tuning anymore, most people have moved on to newer stuff that uses OBD2 but I still have a couple cars that use even though they are already pretty much tuned to where I want them.

 

[vavavroom]

I've seen ECU EPROM rot happen in a couple of late '90s cars.

 

[brianl703]

The PROM in my 1983 G body is soldered to the ECM, and does not have a window for UV light to get in

Later CAL-PAK and MEM-CAL systems were different

At some point PROMs which are basically an EPROM without the window became available. They were programmed like EPROMs but could not be erased. Their only advantage is that they're cheaper than an EPROM. I don't think these were available in 1983 but I don't know for sure when they went into production. Someone who has a collection of old Digi-Key catalogs could probably find the answer to that.

 

[brianl703]

Dead capacitors would be more of a concern.

I read elsewhere that GM used tantalum capacitors in their ECUs, which may fail by shorting, but at least they don't leak electrolyte all over the board and damage it like electrolytic capacitors eventually will.

Also, if the ROM chip has a window, it can be erased, and is an Erasable Programmable Read Only Memory (EPROM). Some chips without windows could be mask-programmed ROM (programmed by it's design, the mask, at the factory) or Electrically Erasable Programmable Read Only Memory (EEPROM). And, as mentioned previously, there are ROMs that are programmed like an EPROM but don't have the window to erase them, which makes them cheaper.

All of these except for mask-programmed ROMs rely on electrical charges being stored in cells inside the chip, and these electrical charges can leak away over time resulting in "bit rot".

 

[brianl703]

Solder failure is big. IDK when they cut down on the lead in solder but they had some growing pains when that happened.

Sometime in the mid to late 90s is when I first started seeing "ROHS" on components, so I would guess that is when the lead-free solder push started.

 

[brianl703]

Almost never happens on GM ECMs. And yes, they used regular EPROM for most of their OBD1 ECMs all the way through to the mid 90s when the switch to OBD2 occurred in 96. My 95 Tahoe and K3500 truck both had the MEMCAL with EPROMs. I still have a bunch of old EPROMs laying around for tuning these vehicles, don't see much use for them anymore these days as there are cheap EEPROM and FLASH style replacement chips that are quicker and easier to use. 2732A, 27C128, 27C256, and 27C512, they were all used in various years and ECMs but almost all the 27Cxxx are soldering into a MEMCAL unit that also has some other circuitry on them.

Supposing I wanted to back up the ROM in an 80s GM vehicle, what's the cheapest way to do it? Presumably I'd have to desolder it from the CALPAK.

 

[nthach]

With Euro cars its called RoHS, when they started that crap electronics reliability took a big hit. After 02 I believe it is also applicable to domestics too.

There is something called Taiwanese and Chinese Capacitor Syndrome from 1998-now. It was a case of corporate espionage, an chemist for one of the Japanese capacitor makers(Nichicon, Nippon-Chemicom and Rubycon) went back to Taiwan or sold the electrolyte recipe to one of the Taiwanese/Chinese manufacturers. The stolen recipe was missing an ingredient to inhibit aluminum corrosion.

Soon after, people in the overclocking world saw capacitors give out. Eventually Dell, HP/Compaq, IBM/Lenovo had those issues as well(all the PC makers use Asus, Foxconn or MSI motherboards) and it spread to the automotive world - there was a former Denso engineer advising people with late 1990s-mid 2000s Lexus models to check their ECUs for bad caps. The automotive world still uses electrolytic capacitors - solid capacitors are in use as well.

Bad caps still plague electronics to this day. At the least, a bad cap will cause system instability. At the most, fires. And in many cases, since the corrosive electrolyte leaks onto the PCB, the board is damaged via eroded traces or corroded solder pads.

 

[brianl703]

Bad caps still plague electronics to this day. At the least, a bad cap will cause system instability. At the most, fires. And in many cases, since the corrosive electrolyte leaks onto the PCB, the board is damaged via eroded traces or corroded solder pads.

Even capacitors from before that time will eventually leak (it's just that the bad ones leak much, much sooner). Shango066 on Youtube made a recent video about an ECU from a 1992 Ford F-series that had capacitor leakage, and it really damaged the board.

 

[michaelluscher]

At some point PROMs which are basically an EPROM without the window became available. They were programmed like EPROMs but could not be erased. Their only advantage is that they're cheaper than an EPROM. I don't think these were available in 1983 but I don't know for sure when they went into production. Someone who has a collection of old Digi-Key catalogs could probably find the answer to that.

I remember hearing a rumor that GMs demand for the Motorola 68000 microprocessor had an effect on the launch of the 1984 Macintosh

Some B roll of inside one of these ECUs courtesy of a 1981 Laserdisc

 

[brianl703]

I remember hearing a rumor that GMs demand for the Motorola 68000 microprocessor had an effect on the launch of the 1984 Macintosh[/MEDIA]

Wonder what GM was using it in, a 68K CPU is way more powerful than what an 80s-era ECU needs.