Dakota digital/Gm controller OBD2 issues.

[Sean1985]

I have an ls3 with a gm controller in my 67. I have the Dakota digital bim module that connects to the obd2 port that feeds my tach and coolant temp. Every time my electric fans kick on I loose the signal from the ecu? The bim module doesn't loose voltage. This just started recently. It haven't always done this. I talked to Dakota digital and they said the module either works or it doesn't.
Has anyone had this issue. It has a brand new battery and I'm not having any kind of crazy draw on the battery. It has to be some sort of signal from the ecu? I appreciate any feedback.

[Hart_Rod]

I would recheck all of my grounds.

[clinebarger]

How are the Fans/Fan Relays wired?

[Sean1985]

They wire right off the fuse box that's provided in the gm harness. It's controlled by the ecu. It's a crate ls3 and a gm harness. So they leave a pigtail for the fan to splice onto. And the ground is connected to the same ground as the chassis, and everything else. I think next I'm going to look at the fuse box relays, and fuses. I know these fans draw a lot of current.

[knomadd]

I'm sure your Dakota Digital box isn't grounded to the same ground on the chassis. You'll want to check ALL of your grounds to be sure. The relays might be a good place to look too, but intermittent things can often be traced back to a bad ground somewhere, especially if it didn't start out with the problem. Otherwise, just a guess, it might be something to do with the signal you're getting form your DLC to the BIM module.

Also, check to see if your fan wiring is secured in place and hasn't rubbed through causing a short of some-sort.

[Sean1985]

Yea I've checked every ground so I'm assuming it's from the dlc connection. I think I might scrap that and tap off individually to get my tach signal to be 100% sure.

[Sean1985]

Plus why would I loose a ground when only the fans kick on. When the fans aren't on everything works fine. Just thinking out loud.

[knomadd]

Originally Posted by Sean1985

Yea I've checked every ground so I'm assuming it's from the dlc connection. I think I might scrap that and tap off individually to get my tach signal to be 100% sure.

Are you using the BIM module for just tach and coolant temp? Are you losing both (everything) or just the tach signal?

Originally Posted by Sean1985

Plus why would I loose a ground when only the fans kick on. When the fans aren't on everything works fine. Just thinking out loud.

If it's loose, or if it's not a good clean ground, the fans could possibly jolt the ground loose, or cause a load that cannot overcome an inefficient/poor quality ground. Or, maybe the fans are the problem? Again, guessing with the fans.

[Sean1985]

Originally Posted by knomadd

Are you using the BIM module for just tach and coolant temp? Are you losing both (everything) or just the tach signal?




If it's loose, or if it's not a good clean ground, the fans could possibly jolt the ground loose, or cause a load that cannot overcome an inefficient/poor quality ground. Or, maybe the fans are the problem? Again, guessing with the fans.

I'm using the bim for both tach and coolant. And yes I'm loosing both. My ground for the fans is the same ground for the fuse box. I daisy chained the ground from battery to motor to chassis to cab. So technically the ground is paralleled through the entire truck.

I think I'm going to disconnect the bim and put a meter on the signal for coolant. That should increase in voltage as temp goes up. And then see if I loose voltage when fans kick on. Then I know it's coming from the ecu. Or too many amps from fans. But not blowing a fuse. Hahaha. Oh the fun of trouble shooting. As if I don't do this enough on elevators.

[knomadd]

I wish I could be of some help. Good luck!

[Sean1985]

Originally Posted by knomadd

I wish I could be of some help. Good luck!

I appreciate the help!

[knomadd]

Did you figure anything out?

[Sean1985]

Originally Posted by knomadd

Did you figure anything out?

I had a fuseable link that wasn't letting 12vdc pass. It was like 11 and some change of even a little less. So the voltage drop was too much for the bim. But everything else was working fine. I had the same voltage running to all the Dakota digital gauges. Weird. But got it fixed. Thanks for the help!!

[knomadd]

That does sound weird. Glad you got it fixed!