Sudden parasidic battery drain

[rustfarmer]

2001 QX4 had been working fine but after sitting a week, battery was totally dead = 0.0 volts. managed to charge battery but seemed suspect so since it was under warranty I swapped it. Upon installing the new one I checked for amp draw and found what appears to be a 6.7 amp draw with everything turned off. Alternator was replaced about six months ago and had been working fine but this seems weird although the temps here have been kinda high. I will pull fuses one at a time tomorrow but this seems an awful high draw for some minor circuit. I will also see if I can disconnect the main alternator wire to see what that does. All ideas most welcome.

[VStar650CL]

Alternators don't usually short through the main terminal. In theory they can, but usually they short through a diode or field winding and draw about an amp. Radios are prime culprits for draws as well, both the head units and amplifiers, but those also usually draw no more than a couple of amps. For a 6 amp draw I'd think you'd be looking at something in the engine box, maybe a stuck ignition relay.

Note that your ride has an SEC (Smart Entrance Control), which is the prehistoric ancestor of the BCM. The SEC is always awake, so you can't get an accurate draw estimation without letting it hibernate. Modern Nissans mostly hibernate at 30 minutes on the dot, but earlier implementations usually time out at something between 10~20 minutes.

[rustfarmer]

Thank you for this info. What items will prevent the SEC system from going into sleep mode? Must the hood be shut? Windows? Others? I do have the hood open.

[VStar650CL]

The hood being open shouldn't bother it, or windows. The doors need to indicate shut, so I usually pull the switch off the door nearest the fusebox so I can get inside to check things without waking it up.

[VStar650CL]

Oh, PS - On steel key vehicles, the key needs to be removed from the cylinder.

[rustfarmer]

Thanks very much Vstar!

[VStar650CL]

[rustfarmer]

The plot thickens! No relays seem to be at fault, but when I pull the 40 amp ABS motor fuse the drain goes away. I haven't been able to find a shop manual at the local parts stores so don't have a wiring diagram. Any idea what all is on this circuit or what commonly fails? Are wiring diagrams available here somewhere?

[rustfarmer]

PS: No signs of rodent damage (fingers crossed).

[VStar650CL]

There's a complete FSM here in Nico:
https://www.nicoclub.com/infiniti-service-manuals

ABS controllers can fail short, and the solenoid drivers are a big draw that could certainly account for 6A.

[rustfarmer]

Thanks again!

[rustfarmer]

Well rats! I had the thought of hooking everything back up and then driving the unit around in a field testing the ABS system in hopes that it might release the stuck part, so first I test that the draw is still happening after sitting overnight with the battery disconnected. As luck would happen, the draw is gone and all i'm getting is about 12 milliamps which I consider normal. I hook things up enough to go for a drive and find that the shift interlock doesn't release! I pull the fuse for that and it's fine, so I use the manual release and proceed to drive around a field on our property doing fast hard stops to trigger the ABS and it works just fine. No codes or lights on dash and brakes seem just fine. Back to the shop and test the battery drain again and still just 12 milliamps. The shift interlock still doesn't release. I check the pedal switch and it seems there are two. The one I can actually see seems to not move when the pedal is depressed so I guess I'll remove it for testing next. SUCH FUN! These two systems seem to have nothing in common so much head scratching going on.

[VStar650CL]

6A is about right for brake lights, and a sticky switch would certainly cause a dead battery. The brake switch should have Red/ Black and Green/Yellow wires, the other one is for the Cruise and can't really cause issues in other systems. Red/Black should be hot all the time, Green/Yellow should go hot with the pedal. Check the rubber stopper on the pedal, too. If it's disintegrating it can catch the actuator and cause the switch to work sometimes and stick other times.

[rustfarmer]

Thanks again. So neither pedal switch has anything to do with the shifter interlock? Fuse for the interlock is good. What else should I check since it suddenly won't shift?

[VStar650CL]

No, they are related. The interlock solenoid is powered by the brake switch and grounded by the park position switch inside the shift mechanism. So if there's no power through the brake switch to the lamps, there won't be power to the shift lock solenoid either. See AT-266 here:
https://www.nicoclub.com/service-manual ... ission.pdf

[rustfarmer]

Fantastic Vstar650CL, thanks so much. You are the best!

[VStar650CL]

[rustfarmer]

Turns out both the brake and cruise control bumpers were completely missing. Dorman has a replacement kit which seems to include both a black one and a white or clear one. The clear one is a bit thicker, so which goes where? It looks as if the plunger on the brake switch is black and on the cruise is white. Is it fair to assume this is a color code? Or is the clear one an improved part and thus I should buy two kits and use the clear for both switches? Sorry to be so picky.

[VStar650CL]

I answered in that other thread, but I'll repeat it here. The Nissan part is the same p/n for both stoppers, 46584-5P010. So I'd say use whichever ones seem to fit your present adjustments better. The kit may be different thicknesses for different models and not one for each hole, so one of them may not be intended for your vehicle at all.

[rustfarmer]

Perfect, thanks again.

[rustfarmer]

I'm calling this FIXED! After replacing both rubber switch bumpers I thought I still had a problem but found a bad brake lamp. After replacing that bulb, draw reads 12 ma and everything now works. Reading the wiring diagram I see that one 40 amp fuse feeds both the ABS system, the brake lights and the shifter interlock, so that had me going down the wrong rabbit hole for a while. Thanks for your patience and most valuable help. Funny that I have had a family member ask about this same problem and now am able to help them too. Much thanks!

[MisterH]

I'm calling this FIXED! After replacing both rubber switch bumpers I thought I still had a problem but found a bad brake lamp. After replacing that bulb, draw reads 12 ma and everything now works. Reading the wiring diagram I see that one 40 amp fuse feeds both the ABS system, the brake lights and the shifter interlock, so that had me going down the wrong rabbit hole for a while. Thanks for your patience and most valuable help. Funny that I have had a family member ask about this same problem and now am able to help them too. Much thanks!

It's rather amazing that a failure of what seems like a totally unrelated part can cause such a problem. It happened to me as well and I was chasing my tail for a while until I found the little black hardened rubber piece on the floor underneath the brake pedal and thought, "what the hell is this from?"

[VStar650CL]

Much thanks!

You're most welcome. Happy motoring!