New battery drained

It's so strange reading through this thread as I could be Glider right now.... only difference is that I have an Xtracab 4x. I assume the electrical system would be pretty much the same.

Everything that he is saying is exactly like my situation. I've been dealing with this for a few months now but only recently(yesterday) have I begun trouble shooting it because as Glider said, as long as I drive it once every 4 days or so it's fine. When I go on travel I just pull the terminal but that's a pain(although not as frustrating as having to get a jump it at 5am when I'm half asleep,,,)

Like what was stated above, my plan was to get a amp meter an put it in series with my battery and begin pulling fuses. I intend to start that this coming weekend. I have a number of EEs at my office who enjoy these challenges so I'm hoping to have them help me out.

I'll provide updates as this Scooby mystery unravels on my side.

Cheers,
Dave

FYI:I just found this post from last year in case you havent see it already. https://www.tacomaworld.com/threads/parasitic-battery-drain.539364/

 

Also for a quick fix you could use a Deltran battery tender that will keep it charged when not in use and above freezing in cold weather. I have one on my old car and it works great. Battery is always charged. The kit has a quick disconnect that works great and they make different ones even some that are weather proof. Just a thought . Talked my neighbor into getting one for her 84 ramcharger and it never fails to start.

 

Have your alternator tested. It's free and it takes a few minutes at a local Autoparts store.

 

Thanks, but I already had it checked when I had the battery checked and also replaced. Dealer told me it's possibly the E.C.M..I think that's what he said. Anyways that's real expensive so I might be down to that. Ughhhh !!!!

 

Thanks Sramirez.
I haven't had my alternator checked but I would think my battery would die rather quickly if the alternator was bad. This battery was installed in Dec, holds a charge, and works fine as long as I run the truck every 4 days or so, (or if I disconnect it before letting it sit).

 

I’ve heard of the voltage regulator inside the alternator going bad, which can cause parasitic drain on the battery. Run the truck and shut it down. Check the voltage after about 30 minutes. Disconnect alternator electrically. Check battery a day later and see if power drops. If not, it’s likely a bad alternator.

 

I use a test light. Connect one end to the disconnected positive battery terminal and the other to the battery terminal. How bright it illuminates is an indication of voltage being drawn. Some of the large current sources like the 120 Amp alt are bolted inside the engine compartment fuse box. There is usually a large red/black wire from the alternator that bolts to it. Disconnecting this wire eliminates the alternator as a problem. There are diodes in the alternator(+ and -) and depending which one(s) go bad can either drain the battery or not allow it to charge fully. Follow the flow chart and you should be able to narrow it down pretty quick. It could be something a simple as a auto door lock switch being bad or something like a parasitic drain across the top of the battery to the hold down brackets.

 

Thanks Glamisman! That pdf is just what I was looking for. I just hooked up my amp meter and confirmed there's a 203-216mA draw with doors closed/nothing on. What is interesting is that the current jumps from a steady 203 to around 216 every 8 seconds.

I'll post an update of my findings...

Cheers,
dpw

 

By chance does anybody know what the current draw should be for a "clean" electrical system? (either with alarm on or off) I've found the general comment that cars shouldn't have a pull greater than 50mA. I didn't see any mention of this in the FSM but I might have just not found it yet.

When I pulled the 15A dome light fuse the current dropped from the fluctuating 203 to a steady 25mA (with the dome light on the pull is 750mA.)

The fuse looks good and I've switched it with another 15A with no change.

To be continued...

 

50mA is considered "acceptable". While this is a generalization I have no way of knowing what your vehicle is equipped with... aftermarket radio, alarm etc. Different manufacturers of aftermarket accessories might build into their product a delayed "sleep" cycle. What you might think is a draw will disappear after 30 minutes when it goes to sleep. The same thing goes to different auto manufactures. Sometimes you just have to put a recordable mA meter on the battery and wait 1/2 hour to see if all the modules have gone to sleep. If you forget and open the door, quesss what, you have to wait another 1/2 hour.

as to your dome light draw, does your truck have a glovebox light?

 

Thanks Glamisman,
Its a stock truck with no mods so I was just curious what a stock '03ish tacoma might show.
I do have a glovebox light but it's never worked--I've had this truck for almost 10yrs and this parasitic draw issue just recently started so I'm not thinking it has anything to do with the gb light. I just did a search on the glovebox light and found a funny thread about how many 1st gen owners didn't know they had a gb light. https://www.tacomaworld.com/threads/glove-box-light.309627/

It's looking like I might have the same issue as the member that previous post I referenced--which unfortunately doesn't come to a conclusion,,,yet. https://www.tacomaworld.com/threads/parasitic-battery-drain.539364/

 

Dealer is saying the e.c.m. is most likely the problem. So,,,I drive it about every 4 or 5 days and everything is good. My truck was mainly to be used for weekends to pull my small boat and trailer and the occasional trip to the lumber yard, while my Solara ( which can go a month without battery issues) is my daily driver to and from work.

 

Later rigs, 2nd gen and up, get towards the 40-50mA.
My 99 V6 ex cab with no alarm or aftermarket parasites runs 10mA and has for 20 years.

 

The dome fuse usually supplies power to the clock and radio (presets, etc.). 178mA seems excessive. You might try disconnecting the clock and radio to narrow down exactly what's drawing the current.

 

Thanks, I'll look into how easy that might be, but judging from the wiring diagram I don't think they are on the same circuit.

-------------------------------------------------------

So, I'm giving up for today--after about 5 hours of effort no joy. (~5 hrs of trying to read the FSM, researching online, and troubleshooting at the same time).

Here's the summary:

• Confirmed a parasitic draw of ~203 mA. (with everything off, closed, and sitting)
  
• Found that it drops to ~25mA when I pull the 15A dome fuse.
  
• Dome is in the off position. (kicks the draw up to around 750mA when I turn it on)
  
• Pulled all the other fuses(because it's easy to do) and confirmed that that didn't change any thing with respect to the 203mA draw

Not sure where to go from here... I'm guessing to check for shorts or bad relays by following everything that touches the 15a dome wiring circuit with resistance measurements. That or just take it to the dealership.

What a pain.... luckily this is more of a frustrating problem than a serious problem.

I'll make sure to update with any progress if it happens.... or I just call it good and live without interior lights (that's what headlamps are for right?) haha

 

dpw... I highly suspect that your drain is in the Body ECU. Body ECU's stay awake for a while after you exit the vehicle. I would open the windows and shut all the doors put the meter on it and walk away for at least 1/2 hour. If the draw is still there I would start pulling door light switches as I suspect that one of these is telling the body ECU that a door is open when it isnt. If it was me I would pull the 2 wires from the Body ECU to the interior light circuitry and check again. I might even consider cutting those 2 wires depending on what else they go to, if that doesnt solve it they can always be soldered back together.

 

I never heard of the Body ECU. Does Toyota call it something different?

The power source pdf that you (Glamisman) posted lists these things on the DOME fuse circuit:

Cigarette Lighter and Clock
Combination Meter (w/ Tachometer)
Door Lock Control
Interior Light
Key Reminder and Seat Belt Warning
Light Auto Turn Off
Power Window
Radio and Player

So pick whatever of these are the easiest to get to and start disconnecting connectors to see where the current draw is.

 

Thanks all. Looking at the wiring diagram of what's downstream of the 15A Dome light, I agree that the ECU (or something feeding it) is the most likely suspect. I did pull the fuses on the ECU without seeing any changes in the amps. Good idea to start pulling the incoming wires to the ECU, I think that will be my next step. (looks like DrZ also suggest this route)

I did close everything up (except the hood) and watch the amps. I let it sit for at least 30 minutes or longer (I was reading and trying to piece together the various sections of the FSM). It looks like after about 2-3 minutes the something happens and the draw drops about 10/15mA and then it sits around the stated 203mA level.

What I'm realizing is that there is more to the wiring diagrams than what I'm seeing... So while I thought the clock and radio was not part of the dome circuit, based upon the drawing, it in fact is connected somehow as they don't have power when the 15A dome fused is pulled. (so apologizes to DrZ I am either not reading the drawings right or not seeing the right drawings... perhaps both!

I pulled the 15A fuse and the following did not work (i did this to confirm what I need to check as a possible parasitic source):

• No Clock
• No Radio
• No personal lights (LH or RH)
• No Dome light
• Door locks,,,:
  • With car key on: power doors locks work fine both ways (lock/unlock)
  • With car key off, the unlock button works on the driver door only. (This might be by design, but seems strange...)

Worth noting what does work with the 15A fuse out:

• Cigarette Lighter
• Power Windows

Obviously, I'm not doing this in a completely exhaustive method and perhaps that's part of my challenge. I figure(hope) that eventually the source will become clear as I trip my way through this.

Thanks for your time....

/dpw

 

Check out DaveInDenver's post regarding the ECU.>> https://www.tacomaworld.com/threads/parasitic-battery-drain.539364/

 

The diagram that I posted is very different than the one dpw posted... his, a 2002?, clearly shows "Body ECU" where as the '96 has no such critter.

dpw, is that what the FSM states, 200mA is acceptable?