FICM voltage decreases under load

[motorhead440]

Key on 48.5 vdc.
Cranking 48.5 vdc.
Light throttle 48 vdc.
As load increases voltage drops. I have seen a low of 32 vdc while towing 11k up a long grade in 90 degree heat. Is this normal?? Voltage as seen on my CTS

[southend]

Absolutely, not. Ficmrepair.com, and load test your batteries.

Sent from my phone that somebody didn't help me get.

[motorhead440]

Honestly , beyond watching the voltage fall on my CTS, I am seeing no negative effects. Truck runs great , quick starts, a minute or two of stiction in the cold months. It gets great mpg, 15.5 city, 19 - 21 hwy and 12 - 14 towing 8k boat 10 k camper.

I'm concerned if I touch it, well , things may change.

I have not found anyone describing a similar FICM behavior.

Thoughts ?

[colo_dually]

If you are seeing voltage drop, you're risking your injectors by not correcting the issue.

Since its when its running, under engine load, I would have your alternator and your batteries load tested and replaced before touching the FICM.

You have a few options when you do, have FICMrepair.com rebuild it, get a remaned unit (both of which will fail again), or step up to the power supply and heat sink from BPD and fit it to your current logic board (and not worry about another failure).

[PGreenSVT]

What Ben said.

[motorhead440]

Hmm good points. Batteries are brand new ,less than a month old. Original alternator 134k miles. Maybe I should start there.

Thanks

[Korx]

Send it to Ed at FICMrepair.com, I just did the same thing today.

If you end up taking it out I found it was easiest to remove the whole air filter assembly and drop the coolant reservoir in the spot where the air filter was. I realize this isn't necessary but it added a lot more working room and I didn't have to drain any coolant.