Following ECBM rebuild multiple cluster faults

hbomb2k · February 16, 2020

Hi everybody!! New member and long time chevy enthusiast here. I have had a 94 LT1 M6 Firebird for a while, that I use for drifting and was in need of a tow rig. A friend's 99 1500 came up for sale and I had to get it, still chasing down a few small issues on the truck, though it has been good to me so far. Truck has 261k, a fresh motor with a stage 2 texas speed cam and a 80k mile trans with a Yank 3,000 stall converter. Its tuned and has all the supporting mods as well as a clutched LSD in the rear and a leveling kit and some wheels and tires. Makes about 330 whp and is an absolute riot around town despite the 8 city mpg on 93 octane.

I bought the truck knowing it needed the ECBM sent off and "rebuilt." It was throwing the CO265 code and a loss of communication code. The ABS light and Red brake light would be on.

Upon getting the module back I installed it and came to find that when I plug in the ECBM 16 pin connector a multitude of cluster faults occur:

The ABS light was still on (though I havent had a chance to clear the codes yet)

The red brake light no longer came on at all, even with the parking brake depressed (it used to work)

The fuel gauge reads empty when the 16 pin is plugged in (used to work perfectly fine)

Security light flashes while driving. Doesn't normally do this.

Lastly the little squares that indicate what gear you are in do not work either.

I got the ECBM serviced by a repuatable place, that has a warranty. I am inclined to think that the ECBM is not the issue and that now that the ECBM is finally repaired (hasnt had a working ECBM for at least 4 years) it is revealing a problem in the cluster.

I know grounds are an issue, ive checked the one underneath the drivers door, are there any others i should check?

Would it be worth testing continuity between the 16pin connector and the gauge cluster pinout??? Im thinking that could lead me in the right direction.

The 16 pin connector has been unplugged for a very long time, it could be that corrosion is causing a bad connection here too.

What is the connection between the ABS module and the cluster that would cause such a wide range of faults?

Is it worth throwing a rebuilt cluster at it? Ive been eyeing the 7 gauge ones out of the 2500s so that I can have a trans temp gauge. Though im not excited to shell out $200 not even knowing it would fix anything.

If it helps here is a video showing what is going on:

davester · February 16, 2020

What do you mean by "checked the one underneath the drivers door"?

As for the IP, it's common for bulbs and stepper motors to fail. I believe if you swap clusters, you need one from '02 or earlier, as the computers systems were re-jigged in '03 (or thereabouts) in an incompatible way with earlier trucks. And the cluster stores the mileage, so that will be off.