Dean Fritz

Did you ever find out any more on the limp home chips? Are they resistor banks like you thought?

Grumpy

On the C3 ecms they use a calpak, and on the memcals it's a netres

Network resistor.
It allows the RFD a set of resistor for fueling (RFC = redundent fuel devise).

Dean Fritz

Can a person buy the the correct resistor network?

Dean Fritz

I was doing some investagating with 1 of the memcals I had and found 2 chips under the ESC Filter, one was a 14 pin package (16060954 - 90 37) and the other was a 16 package 16060956 - 90 38). These look like GM part #'s. I think this Memcal Came out of a 87 Calvalier.

Grumpy

One is part of the ESC and the other the netres

gravitar

I haven't uncovered any further info other than the afore mentioned, I'm getting my info from the gmecm list which many of those posting here are active members of!

Grumpy,
"On the C3 ecms they use a calpak, and on the memcals it's a netres"

I'm familiar with the concept of a resistor network, but what exactly is a calpak? The C3s don't have a socketed "limp-home" chip, do they? I was pretty sure the only socketed/app-specific component was the EPROM on a C3.

Grumpy

On some C3s the netres is serviceable, and called a calpak.
On the memcals it's sholdered in, and just part of the memcal.
Either way it's about the same piece. Er, in function it's the same. Resistances var from apllication to application.

I just don't worry about them.
I carry a spare ecm, and proms with me. Just seems like I always have something to try..... LOL

Blade

I wonder why GM felt the need to add a netrese/calpak to our carriers. I mean, have you guys ever heard of an EPROM chip failing ? I've never heard of anyone having one fail and having to rely on the calpak to get home

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92 Z28 L98 350
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Ported and polished heads, ported stock TPI base, ported plenum, Comp Cams XR270HR-10 cam (lift .495/.502 duration 218/224 lobe separation 110), Edelbrock TES headers, LT4 valve springs, Crane AFPR, Flowmaster catback with LT1 style tips, MSD coil & wires.

Best ET 13.5@105 mph

"Take that auto, drop it in first, hold the brakes, stomp the gas and grin from ear to ear! :-)

http://www.truspeed.dhs.org/Members/...dmondIndre.htm

Grumpy

When I was working at the dealers it was not at all rare for something to come in with a prom failure. Has gotten alot better, but in the mid / late 80s was a nightmare for a while. Don't forget this stuff is all based on work from the 70s. I don't know about the flash PCMS but you can still see patchs from the 92 stuff that was in the 85 stuff.

gravitar

It may not be so much the PROM failing, but some other part of the digital circuitry. It has been said on the list that the limp-home circuitry works in lieu of all (or nearly all) the digital components. My guess as to WHY they included this infrequently-used circuitry is for one thing: LIABILITY.
It's just like with the industrial stuff I work on, OSHA expects that equipment failures will fail to safety, not fail to danger. In other words, if you interrupt a stamping press, will it continue travelling toward a pinch point? No, it must cease all motion in some finite, predictable time frame, or travel AWAY from any possible pinch point that could cause harm to the operator. On a car, if your computer takes a s**t while you're on the highway, do you want it to stall, leaving you without power brakes, steering, etc? You'd want some way to maintain a minimal amount of drivability for you to (at least) get off the road under driver control.
Nevermind the fact that maybe only 1 in every million cars sold will have an ECM failure while under load, That one-millionth car owner will be a P.R. disaster for GM, if not worse.