Nvram battery life

[antus]

Agree. Also worth noteing the nvram is intended as a tuneing tool, even though people do run them full time for years. In a perfect world you'd buy an eeprom and write the tune to that and put it in a memcal with a socket and call it done, then it'll never go flat or get erased for whatever reason in car.

[Rhysk94]

I've still been chasing this Code 55 problem from 2024.
Most of the time I do NOT get any codes.
I've had a Code 55 before, and another one today.

Code 55 ECM Failure
Check all ground connections of the ECM. If all are OK, replace ECM.

Very random. Can be weeks between the problem arising.
Most times there is NO issue with driving and everything works normally.

Until: Car drives fine. Park and do your business.
Come out to start car, turn key to RUN position - CEL (Check Engine Light) flashes once and goes out.
THAT is not correct. CEL should remain ON until engine starts and runs.
If you start engine now, it stalls after a couple of seconds, over and over. Won't stay running. NOT driveable.

Get towed home intending to trace and fix the problem the next day.
Next day, put the key in and everything is back to normal.
CEL comes on and stays ON until engine starts (as it should).
Car drives normally again - until the next time the problem arises.

Yes - I have checked wiring over and over. Can't find anything visually or with testing wrong.
I've swapped in spare ECMs with no change. Everything was working fine for 10 years prior.

But obviously an intermittent problem somewhere.
Someone suggested that my NVRAM battery is close to dying.
I'd expect a "good or dead" battery - not a "slowly dying" scenario where the next day it's fine.

What car is it in?
If vt,vx,vu I have my money being on its wiring.
Factory constant 12v crimp always fails on them in the loom right near the 3x plugs.

If it isn't one of those cars, then does the issue stull occur with a normal memcal in it ?

[Tony B.]

What car is it in?
If vt,vx,vu I have my money being on its wiring.
Factory constant 12v crimp always fails on them in the loom right near the 3x plugs.

If it isn't one of those cars, then does the issue stull occur with a normal memcal in it ?

1987 Pontiac Fiero GT
I don't have a "normal memcal" for this. Nothing is stock.

While investigating today, the only "iffy" thing I can find that may be an intermittent is this.
The Black wire is a ground directly from D1 of the ECM.
Looks like it's been stretched and the wire could also be internally frayed?

[Tony B.]

Progress. Made new pigtails that I crimped/soldered to the harness.
It was when I was bolting them back to the head, that I discovered one bolt was longer than the other.
This mixup may have happened when I last had things apart to replace the clutch.

I measured the hole depth, and yes, it is possible the bolt was bottoming in the threads.
(this may have been the problem all along - bolt is "tight" but not actually clamping wiring eyelets solidly to head)
I replaced it with a 1/4" shorter bolt to match the other and used star washers.

So far, the car has been driving fine. ECM is not complaining about a "bad ground".
As I mentioned before, the CEL problem and Code 55 was very random.
(2 of the 4 wires are grounds directly to the ECMs internals)

Been driving around for almost a week now. NO ISSUES.
I think the problem has been solved. <fingers crossed>

I'd have discovered this sooner had I removed both ground bolts, instead of just tightening.
Since they were "tight" I was convinced the grounding was good. It wasn't on the long bolt.

[Tony B.]

Not so fast... I had always suspected the grounds were never the problem...

I was fixing some lighting issues on the car.
While I had the ignition on the ON position, the CEL light went out!
This also threw a Code 55 again - back to bad grounds, or bad ECM

The problem also "resolved" itself during repeated ON/OFF cycles of the ignition switch while I sorted out the lighting problem.

I decided to proceed with my earlier plan of rechecking the ECM wiring with an ohm meter and voltage tester.
Particularly, the "power side" of the equation. I disconnected the ECM connectors to probe the connections.
All the ground connections A12, D1, D10 to the ECM tested good with the ohm meter.

Battery voltage was 12.35V
ECM connections B1 and C16 are direct from the battery and also read at 12.35V

BUT ECM connection A6 powered from the ignition switch only read 11.71V
It was only reading 11.71V at the ECM fuse as well. A 0.64V drop.
Diagnostics online indicate the ECM is not happy with a variance greater than 0.30V

I dropped the steering column to get at the ignition switch.
It had 12.35V going in (main Red wires from battery), but only 11.71V coming out (Pink wire to ECM fuse circuit) with Key On.
Thirty-nine years and +230,000kms (143,000 miles) had a lot of Key On/Off cycles and hours of driving.

There was likely wear and/or burned contact points in the switch. Voltage passing through would vary (a test light wouldn't reveal this).
It also explains the randomness of the problem and why Key On/Off or pulling/reinserting the ECM fuse sometimes "fixed" it.

So I replaced the ignition switch with a new one.
Power in and out are about equal now, less than 0.03V variance.

Here's hoping I have finally SOLVED the issue.
It's been almost a week with no further issues. Thank goodness.