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Discussion Starter · #1 ·
Hello, I am wondering if I am testing my battery drain issue incorrectly.

I have read numerous posts about sleep mode being engaged after 20 minutes. However, how do I know that when I am pulling fuses and testing the current draw on the battery that the computer is in fact not in sleep mode yet?

My current process is as follows: I shut the ignition down, wait two minutes, disconnect negative battery cable, hook one end of multimeter to negative battery post, hook the other end of the multimeter to the negative battery cable, and get my current draw amount in Amps, disconnect multimeter, open passenger door, pull a fuse, close passenger door, hook multimeter up, get reading, and repeat.

Is it possible that the computer is coming on each time I hook the multimeter up? Should I be connecting the multimeter with the clamps and let it sit there hooked up to the terminal post and cable for 20 minutes to be 100% sure it is in sleep mode before I pull fuses??? :???: :???: :???: :???:
 

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Yes I would use clamps on my amp meter. It's to bad an inductive amp meter is not sensitive enough to so you can leave battery hooked up. You can then sit in passenger seat and pull fuses till amp draw either lowers meaning more than one draw or goes to 0 and you found the curcuit. Then you need to determine if the parisititcal drain is normal and battery is weak or if there is a slight grounding of that curcuit not enough to heat up an burn the fuse but has enough resistance in the ground to just drain the battery.
 

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Discussion Starter · #3 ·
Ok so in order to determine the real drain, do I need to hook up the multimeter and wait 16 minutes for the ECU to go to sleep and see what the drain is at that point? Am I waking the ECU every time I re-hook up the multimeter and defeating the purpose of my test?
 

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Newer inductive clamps are very accurate, and preferred for testing quiescent drains, because you don't break the circuit, which you can do with a meter inline too. By breaking the circuit, you are resetting everything, which can cause issues with things being properly asleep, or even hide a problem of something not shutting down properly.

To start, turn on your window lock, so it has a little red LED lit, turn off the key and open and then manually latch your doors and upper tailgate, open the glove box, and remove it's bulb, and pull up slightly on your hood switch to put it in service mode, then what you want to do to use a meter inline is loosen the negative post and connect one end of the meter to terminal. Then without losing contact with the battery, slide the terminal to the top of the post and clamp the other end of your meter to the post before separating the terminal from the post. You don't want to connect the battery using the meter, as you can easily blow the fuse in the meter(if you have a mA setting, and separate input to the meter, the fuse can be too low for initial wake up and interior lights) Now you're reading your drain, and have access to everything you'll need.

To go through figuring out what circuit it's on, wait until the BCU is asleep. You can tell this when the window lock LED, and the shifter's Park LED turn out, when it does, your drain should be under 50mA, depending on year, spec is lower but under 50 will take a while to drain a good battery. Now start pulling fuses and watching your meter, but give it a little while between each fuse to allow anything to then shut down(a minute should be fine, as long as the BCU did go to sleep initially.

If you start with the mega fuses, you can then easily narrow down what other fuses you need to inspect, as opposed to pulling a ton, but you may need to wait for the BCU to go back to sleep. If a fuse has no effect on drain, it should be put back in place, and watch the meter/LEDs to make sure reinserting it didn't cause something to wake up.
 

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Discussion Starter · #5 ·
Thanks RoverGuy this is extremely helpful!

I will get the clamps ASAP and report back.
 

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Discussion Starter · #6 ·
UPDATE: I hooked up the multimeter to the negative post and terminal with plastic clamps (did not have luck getting the mini jumper cable wires today), taped it to the windshield, sat in the truck with all doors closed (but glove box open. I did not take bulb out) and waited for it to go into sleep mode. It started with a little over 2 Amps and after about a minute dropped to about .9 Amps. After about 16 minutes (once the window lock light and red light on center console went off) it dropped from .9 Amps to .08 Amps.
I was concerned that the clamps were not holding tight enough, so to double check I went under the hood and I held the multimeter on the post and terminal (the same way I had been holding it when I was getting the 3 Amp reading as mentioned in another thread). After about a minute or two it dropped to exactly .96 Amps and hovered around there going as low as .94 and as high as 1.02 for the next 14-15 minutes. After that it started rapidly dropping to .20's and then stayed at exactly .08 Amps. It was a little challenging to stay bent in that position for 16 minutes and ensuring I did not break circuit but it was the only way I would know for sure. :thumb:
So, as of right now I would say there is no drain at all right? I left the car parked with the battery plugged in. Now the alarm is on. This will be the real test.

RoverGuy, I will follow your step by step process above once I get the other cables (I only had potato chip bag clips :lol:)

After letting it sit for 5 hours I checked the volt meter on the dash and it is at 12.1 (Note: When I checked it 5 hours earlier it was fluctuating between 12.1 and 12.2 at the dash & 12.6 on the multimeter). I am going to leave the battery plugged in and monitor the volt meter. Fingers crossed!


 

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Discussion Starter · #7 ·
UPDATE: After another 12 hours of the truck sitting with the battery hooked up I checked the volt meter on the dash and it kept going back and fourth between 11.9 and 12.0.

I then disconnected the battery and hooked up the multimeter. It fluctuated between 12.49 & 12.50 (A slight drop from the normal 12.6).

I checked the draw again (not for the full 16 minutes) and noted after leaving the multimeter hooked up for 2 minutes it dropped to .6 Amps.

It made me wonder if the car was drawing more with the alarm on. I hooked up the multimeter, waited 2 minutes for Amps to drop to .6. Then had someone put key in drivers side door, turned it to right, and activated the alarm. I noticed a spike in the Amps to over 2 but after two minuted it dropped flat to .6 Amps again (I ran out of time and could not wait for it to go into sleep mode, but it made me feel better that I am getting consistent readings so far with alarm on or off.

I will check again tonight. Anybody out there? Does this sound normal?

How low is too low for the truck to start? I do not want to continue my experiment past this point obviously.

What does a .1 - .2 Amp drop in 17 hours say? Could it be just from me going in and out of the truck and triggering interior lights, navigation, etc... over the 17 hour period without starting the truck and recharging the battery?

My multimeter is brand new. Is it normal for the volt meter on the dash to give a different reading than the multimeter (i.e. 12.2 vs 12.6 after shutting truck off)?
 

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Don't worry about a minor drop in voltage.

What you've described in your past two posts is pretty normal, 80mA is higher than it should be, but isn't killing a good battery in under a few weeks.

Arming the alarm does briefly wake things back up, and will allow things to sleep faster than unlocked. For complete testing, you want to also test in various modes, such as following running, following a key cycle, following disarm, door open without a key cycle.

Under most circumstances, you don't need prolonged tests, just enough for everything to shut down.
 

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Discussion Starter · #9 ·
Ok great, thank you!

My only other question is whether or not there are ever instances of a spike in mA's after the ECU has gone into sleep mode.

Technically, I held the multimeter on for roughly 20 minutes max. Are there other things that happen after 20 minutes? For example an hour later or 2 hours later that I may not be aware of? Or do you think the mA's drawn within the first 2 minutes of the ECU entering into sleep mode is where it will stay?
 

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Things can wake back up, and at times this is normal, the EAS will wake up about every 4 hours to level itself, or if you are in an area with a lot of RF interference, the BCU can wake up sporadically if the RF receiver gets confused with erroneous information. A good example of a draw that will come and go without regard to it being asleep is the FSR. Generally speaking though, draws usually are from something not falling asleep, or shutting off properly.
 

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Discussion Starter · #11 ·
Great thanks RoverGuy! Good to know. Hopefully .08 Amps is sustainable.
 
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