E61 remotes not working
 

Hi - new member looking for guidance. A friend's 2010 Touring's remotes stopped locking/unlocking. Their C2032 disc batteries were fine. Starting was still enabled - but no vehicle door access functions.

A few days later there was a no-start incident with no interior lights and the fob locked in the column slot. Classic dead main battery. But then a few minutes later it started ok?? With that, the car officially became not-trusted.

I was thinking failing battery - I drove the car a while uneventfully. Having just driven a few miles, system charging voltage was above 13v, but under 12 shut off. The battery was 6 years old, its green cell indicator was dark, so I put in a new H8 battery

Next up, the non-working remotes. Internet search pointed to the booster amp in the top of the tailgate. I opened it up - seals were ineffective - water and green corrosion inside. One resistor had disintegrated and the surface of the board was chipped out, taking the trace with it. It didn't look burned, just corroded/frost damaged.

At least a new amplifier is needed. What else should I be looking for? Did the bad amp eat the old battery? I'd hate to plug in and destroy the new battery or amp by not going far enough. Also, will the different amplifier need to be coded to the car? All thoughts welcome. Take care, Arby

Other thing to check is the wiring going into the liftgate. It's very common for these to break from the flexing over time. I'm experiencing this now and my key range is only a couple of feet. On the left side you have the antenna wire, rear defrost, wiper fluid, and some other wires. Power for the rear antenna amplifier come through the right side wiring loom. Most people have problems on the right side is my guess.

dang, that's even more confirmation for why my remote only works right near the middle of the rear spoiler and the defrost doesn't work.

I fixed the wiring on the right side and waited on the left. I have genuine wiring looms but chose to do the splice and add length fix on the right. Has been good few years now and I bent the edges of the metal housing so that they can't bite into the wiring anymore.

It was a fairly annoying job but it's not terribly technical as long as you can splice in the same gauge wiring.