Hi All -

I've got a '99 TrailBlazer with the 4-button 4wd switch on the dash, and it has been having some issues with battery drain.

I've checked the current draw between the battery & the cable terminal with everything turned off (doors shut), and it checks anywhere from 1.5 to 5.5 amps. When connecting/disconnecting the battery, I heard a clicking sound coming from the pass. side floor area, which led me to the TCCM & the relays mounted in it. When I pulled both of the TCCM wiring connectors & the radio batt fuse, the clicking stopped & the current draw dropped to about .5 amps, so that is an issue, but what could be energizing the relays?

My question is: Should the TCCM be receiving any power at all when the vehicle is shut off? I believe the higher draw is a result of the relay(s) on the TCCM being energized, but again, everything is shut off on the truck. There is corrosion on some of the pins in the TCCM connectors, but I did not see any corrosion traces on the board itself that would trigger the relays, or is there another component I should be looking at? BTW - I do not yet have a factory manual for the truck, so I'm flying pretty blind here.

Thanks in Advance for any help/guidance with this !

Brian J

 

Is the 4WD system shifting correctly? I have a '99 with the 4 button system and a couple times I've had the shift motor on the transfer case get stuck (flashing light never stops when shifting) and drain the down the battery. Pulling fuse and resetting the TCCM usually fixed it. You could hear the motor reset the transfer case back to 2WD.

 

Thanks for the response (!), and I think I found the problem. I didn't realize there is a "power up" surge when you reconnect the battery. After trying to figure out what was going on, I noticed after about 5-10 seconds, the relays in the TCCM released, and my current draw dropped to about 600 milliamps, right where it should be.

I didn't realize the TCCM (and possibly other electronic components as well) went through this routine when power is first applied to the system, even with the key off. (hence the 'duh' !)

Sorry for taking up the space, I'm just starting to learn about the myriad of electronically-controlled stuff on this vehicle and have not yet had the funds to get the shop manual.

Greetings to All from yet another newbie to the forum !

 

600mA is still too high. You should be down to around 40mA after 5 minutes.