So I have a customer car that I’ve been trying to diagnose a battery drain on. It will not start if not driven for a few days.

It’s a 2015 Civic 1.8 - sorry it’s not “technically” an Accord but I’m getting tired of registering with new forums.

It has an interstate battery (MT51R) that was installed in May 2023 and so far has tested good using both a load tester and a smart tester. I also haven’t found any charging system problems.

I set it up for a draw test yesterday about 1 PM - made sure all hood and door latches were in the closed position, all accessories were off, and the key was in the office about 50 ft away. Within a few minutes the draw was pulsing from 17-30 mA - I rechecked it once an hour for the rest of the day and every time it was pulsing the same draw.

I rechecked it again in the morning (approximately 15.5 hours later) and it was pulsing from 150-220mA and battery tested weak.

My morning-fogged brain disconnected my meter before I proceeded with pulling fuses, so I’m yet to isolate the circuit with the draw - I just figured I’d ask if anyone has any ideas while I’m recharging the battery and preparing for the next round of testing.

To me this seems to be a situation of a module randomly waking up, but I’m not sure which one or why.

Also, the only code it had was a history code in the gauges module - U1296 Lost comm w/ info display unit.

As always, thanks for the help.

 

Any module can pull that kind of amperage. Once the meter is hooked up, you can wait until you get the draw. You can pull fuses, or try measuring the voltage drop across each fuse using the tabs on the top of fuse. A dead circuit should be close to zero. A live circuit would be ~0.1V. Once you have the fuse(s) that are drawing current, you can look to see what components are on them.

The Honda bluetooth/hands free control module would cause parasitic draws on those vintage vehicles. If the hands free link is on the fuse you find, that would be my first culprit.

You'll have to use process of elmination to narrow down the faulty component. If you have a thermal imaging camera, you can try to find modules that are putting off heat while you have the draw. It might be quicker to find the component vs unplugging each item on the circuit drawing current. A thermal imaging camera is not something many DIYers would have, but sounds like you have a shop, so maybe you have one?

Good luck.

 

Thanks for the ideas - I suspected the draw wasn’t unique to any one module but wanted to ask those more familiar with these cars than I am.

We don’t currently have a thermal camera but I have been thinking about buying a (relatively) cheap one for the sake of trying it out. I’ve heard they can be quite useful for finding the source of a battery draw as well as points of high resistance in wiring.

I’ll update when I can.

 

Well, it looks like another win for aftermarket remote starts. Wouldn’t it be great if people understood the problems that come with these kinds of devices?

For the 2nd round of testing, the draw remained at 150-220mA for more than an hour after setting it up. It dropped to a stable 8mA when I pulled fuse 29.

The diagram showed it provides power to the DLC (as well as the gauges/info display, keyless entry and a few other things), so I gave the driver footwell a visual and was surprised to find the remote start.

To the installer’s credit, you’d never know it was there (but like always, it was scotch lock city ). I unplugged the control module and receiver and reinstalled fuse 29 - gonna check it again in the morning to verify the draw is gone.

I don’t know how long the customer has owned the car, but they didn’t even know it was there.

 

Just wanted to provide final closure - I completely removed the wiring for the remote start and set it up for an overnight test - the min/max recording function proved the draw was no longer present.