Parasitic draw - help needed

[Diagnostic Dad]

We have a 2011 Ford Edge Limited which my daughter acquired in the fall to use at a college.  At school she rarely uses it.  After a couple months she started getting symptoms of a dying battery.  She started getting "battery saver" messages on the display.  After couple more weeks it would not start without a jump.  We figured it was just an old battery so we had her get a new battery.  They did a test of the charging system and said there were no problems.

 

A couple of months later the new battery was dead.

 

When she came home I did some in-depth diagnostic testing.  I put a multi-meter in line with the battery to monitor the current draw.  Once the vehicle is "sleeping" I've monitored the current draw.  The normal steady-state is about 17 milliamps.  The problem comes every 15 minutes.  The current draw suddenly spikes up to 2 amps, stays there for around 10 seconds, then slowly drops down to 1 amp over another 20 second before finally plunging back to the idle current of 17 mA.

 

Note that the frequency is a bit faster when the vehicle first goes to sleep.  Initially the frequency is every 5 minutes.  It takes about a half hour before it goes to the 15 minute interval, but it then stays at that interval for a long time.

 

To try to find the problem I started pulling fuses one at a time and seeing if the cycle continues.  I tried all of the "small" fuses in the engine compartment fuse box first with no impact.

 

I then moved on to the interior fuse panel.  The most significant change happened with fuse 6.

Fuse 6 is listed as "RF module".

 

As soon as I pull that fuse the 15-minute high current draw stops.

 

I figured that this circuit is probably for the remote keyless entry system.  Sure enough, with that fuse unplugged the remote doesn't work at all.

I was thinking she could live with using a key to get in, but it also makes the Start button not work.  In fact, when you hit the button the car thinks it is being stolen and the alarm starts going off.

 

Anyway, more research pointed me at TSB 13-6-18.  This specifically deals with a current draw due to the remote system keeping the electronics awake.  I took it to the dealer and they confirmed we had old software and updated the VMCU to version 2.2.14 at a cost of $140.

 

When we got home I put my multimeter on again, waited the car to go to sleep and then watched what happened.

No change.  Every 15 minutes it's still drawing 2 amps.

 

I'm open to suggestions on next steps in tracking this down as long as it doesn't involve leaving the car with the dealer with a blank check.

 

Thanks

 

[WWWPerfA_ZN0W]

you may actually need to replace the module, they do fail from time to time. usually it is the RKE module not the antennas at fault.

 

every time a new battery is installed the battery management system has to be reset so it can recognize the new battery and charge it appropriately.

[Diagnostic Dad]

Many thanks for the feedback.

 

I found this page describing the parts to some degree:

https://www.quirkparts.com/v-2011-ford-edge--sel--3-5l-v6-gas/electrical--keyless-entry-components

In the section near the bottom there are two modules listed, but one is discontinued.

The first module is listed as a "control module" BB5Z-15k602-N, and the description just makes it sound like a radio receiver.

The second module is just called "module" BT4Z-19G481-F and no description of function is given.

Would you happen to know which is the "RKE" module?  If it is the second one is there a replacement part?

 

I hadn't realized about the BMS reset.  The videos I've found all show a car with a key and not push-button ignition.  I'll keep searching for for a video showing this configuration.

[enigma-2]

Do you have an aftermarket remote system? Any electrical modifications done? Any repairs?

[Diagnostic Dad]

No modifications or repairs.  We also don't keep anything like phone chargers plugged in.  I'd say it is completely original.

I'm going to work on on tracking down the modules so I can replace them on her next visit home from school.

[Machman64]

Hey diagnostic dad, I am having the same exact problem on my wife's 2011 edge. It pulls 2.06 amps sporadically, sometimes it's a few minutes and sometimes its five to ten minutes. It stoos when I pull the rf module fuse. Did you ever figure out what the problem was?

[Diagnostic Dad]

Hi Machman64.   No, we never found a solution.  We tried replacing the RF module with a new one and it didn't help.

I'm limited on the time I can work on it because my daughter normally has the vehicle at college.

 

I did end up finding that the RF module seems to be triggering the current draw, but it isn't the circuit actually drawing the current.  In other words, it seems like when the RF module wakes up, it wakes up other systems in the car which cause the current draw.

I've done a bunch more research on it and the module seems to handle both the remote keyless entry as well as the tire pressure monitoring system.  I'm wondering of something with that is causing the waking-up, but I still don't know how to actually fix the problem.

 

Lastly, I ended up getting Forscan with an OBD2 connected in hopes that I'd find something there, but no luck.  When the vehicle goes to see the OBD interface also goes dead, so I can't see what is happening when the vehicle is supposed to be sleeping.

 

My current plan for a workaround hack is to put a physical switch in-line with the circuits that draw current and leave the RF module active.  That should allow the remote entry to continue to work and once in the car she can flip the switch before starting the car.

 

Hopefully someone will post a solution eventually.

 

[Machman64]

Thank you for your response. My next step was going to be to change out the rf module. But it sounds like that's a waste of time. I will keep working  on it and if I figure it out I will let you know.

[Haz]

Below is a PDF download link to a job aid on parasitic current draw analysis...

 

Parasitic Battery Drain Job Aid.pdf

 

Good luck!

 

[Diagnostic Dad]

Slight update.  Still no resolution to the problem.  We have a workaround in place now where I put a switch in-line with the RF module.  We use the physical key to unlock the door then flip the switch to make the key fob work for starting the Edge.  When parking for the night (or longer) we lock the doors by hand and turn off the switch to stop the drain.

 

On a possibly related note, we kept getting the battery saver message even after a long trip when the battery should be fully charged.  We replaced both of the current sensors near the battery and it seems to have resolved that problem.  The radio will keep playing after turning the car off now.  Unfortunately there was no impact on the parasitic drawl.

 

In doing research it seems like this is not an uncommon problem.  I would have hoped someone would have identified the root cause.  I wouldn't mind replacing a module or two if it fixed the problem.

[Cerberus]

3 hours ago, Diagnostic Dad said:

Slight update.  Still no resolution to the problem.  We have a workaround in place now where I put a switch in-line with the RF module.  We use the physical key to unlock the door then flip the switch to make the key fob work for starting the Edge.  When parking for the night (or longer) we lock the doors by hand and turn off the switch to stop the drain.

 

On a possibly related note, we kept getting the battery saver message even after a long trip when the battery should be fully charged.  We replaced both of the current sensors near the battery and it seems to have resolved that problem.  The radio will keep playing after turning the car off now.  Unfortunately there was no impact on the parasitic drawl.

 

In doing research it seems like this is not an uncommon problem.  I would have hoped someone would have identified the root cause.  I wouldn't mind replacing a module or two if it fixed the problem.

while this would not locate or resolve the cause of the problem, this idea may work as a solution to the battery going dead..

have you considered a solar panel on the dash board to charge the battery while the car is parked & counteract the parasitic draw?