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Does the Renix ECU have one ground circuit or several?

Runnin'OnEmpty

NAXJA Forum User
Location
Southeast USA
After doing some checks, I've found that the Renix ECU and TCU each draw a constant 6ma of current, with the key off. This appears to be normal for the Renix, but if the vehicle is not driven for a couple of weeks, it'll drain the battery noticiably.

I'm trying to switch the ECU off when the XJ isn't driven for several days, because of the steady 12ma current draw. I figure the easiest way is to place a toggle switch between the ECU and engine ground. I've disconnected all the ground wires that are apparent, including the wires connected with the battery ground cable on the block, and still have the current draw.

My question is: Where does the ground circuit to the ECU (and TCU) terminate?

Thanks for any help on this.
 
Thanks JJacobs, that's what I thought. But when I disconnect those two grounds, I still get a 12ma current draw....??? I know 6ma is coming from the TCU, because I've disconnected it and the current drops in half.

There must be another ground somewhere that's common to both the ECU and TCU. Or maybe several. It may be easier to just put a switch in the hot wires going to them......?
 
Yeah - it's usually easier to break the power lead than the ground in a situation like this - there are so many "sensor grounds" that it's probably earthing through all of those.

Dumb question - is there any reason you can't A) hook up a tricke charger (I have installed 50A quick connects in convenient locations for this purpose - so I can hook up a trickle charger or a battery charger easily) or B) you can't put a solar "battery keeper" on the dashboard and keep it topped up that way? Even if you get 1/4 to 1/2A, you're topping off from a 1/80A draw, so that's plenty.

Don't forget that there are also "keep-alives" that feed the radio and the clock module (even if it doesn't work!) and you might have to account for those as well.

Still and all - the "battery maintainer" (AC or solar) is probably about the best solution. If you get the panel, you can velcro it in place on the dashboard and call it a "permanent installation."

5-90
 
Those are all good ideas, 5-90. I actually have one of those solar powered trickle chargers on a Bronco, that sits (outside) as well. I've thought about using one on the XJ; the lighter socket is only powered with the key on, but it would be simple to run a constant hot wire to it.

I've also considered using a battery disconnect, but then I'd either have to open the hood to operate it, or mount it somewhere out in the weather. (Looking for something simple and convenient to operate, like a toggle switch on the dash).

The clock does still work! :eek: Both the radio memory and clock pull about 1/2 a MA initally, and then go to near 0, and they're on a different circuit than the ECM/TCM. This Renix drain bothers me though. I've never had a vehicle that pulled so much current when at rest......

The trickle charger is probably the best idea, if I decide against switching the hot wires to the ECM/TCM.
Thanks for the ideas.
 
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