Keyless starting difficulties...

[X-cellent]

Originally Posted by bigx5er

I have noticed with comfort access on my 2011 that I can make the keyless start not work. Did it by accident.

If I have my keys in my pocket with my iPhone and the iPhone is blocking they keys, the car won't start. Makes perfect sense, so now my keys are in the opposite pocket.

Had the similar issues with mine (2008) - always had to make sure the iphone was in the opposite pocket or else i couldn't get in the car, let alone start it. My buddy has a 535 w/CA and has no issues. CA always seemed to be weak in mine (even with new batteries in fob) and there were times that i'd have to use the remote to get in as it wouldn't open.

[JCL]

Originally Posted by jeremym

My question is...where and how many sensors are in our trucks for CA?

It's weird...when I leave a fob in the center console and take one with me, I can lock the doors. The driver's side isn't supposed to lock if it detects a key is inside the vehicle. The keyfob inside's battery is fine so it's not like it's just a dead battery and the truck doesn't detect it.

Do we have a few sensors inside the truck in order to triangulate the position of the keyfobs? Or is it just one that uses some sort of radio measuring to detect and pinpoint where the keyfob(s) are?

There are nine antennas.

Four exterior, one in each exterior door handle.
Five interior; one in each front footwell, left and right, two in the trunk (left and right), and one in the trunk centre.

Each covers 2 meters. These antennas also have transmitters built in.

I would change your second paragraph. The vehicle isn't supposed to lock when the key is left inside the vehicle. When you leave a key in the vehicle, I don't believe you are locking the vehicle with the key left there. You are locking it with the one in your pocket. Each transmitter is sending encrypted messages.

Also, the fob transmitters have two stages of low battery, first the warning, then the shutdown (and data retention).

The vehicle receivers also have multiple modes, governed by the sleep status of the vehicle. The sensors in the door handles are duplicated, with both capacitive sensors and Hall sensors. As the vehicle goes to sleep, the capacitive sensors are switched off. The remote transmitter fob doesn't always transmit. It just waits. When you touch the door handle, a wake-up request is sent. Then a message is broadcast from the door handle to ask which transmitter is out there. The transmitter sends back an encrypted message identifying itself. The vehicle then acts on that. All this is by way of saying that it is far from a simple "open" command from the fob, it is a wake-up routine involving a dedicated bus in the vehicle, and this bus is designed to be asleep to save the vehicle battery. Or try to.

And people wonder why these vehicles get flat batteries.

Related to the last post above, if the fob button works but the Comfort Access is weaker, I wouldn't look to the fob, but rather the circuitry on the vehicle that wakes up the Comfort Access, and which transmits a request to the fob. If the fob can send an open signal from the unlock button, it can probably send a coded response (same battery). It just has to be asked for that response, and perhaps hasn't been asked yet.

There are documents posted here with the full Comfort Access schematics and technician training notes. Interesting stuff.

[ALE53]

Good job JCL!

Well, after a flawless first week and long roadtrip, some bad news, on Sun the car AC suddenly got warm, & started to overheat, so I immediately shut it down. Aux fan inactive. Towed to my Indy. 2d time for the fan relay, and first time the fan was replaced. Then the battery starts draining. New battery installed. Seems my e70 won't go to sleep now. I have a MOST (or is it CAN?) BUS module that is an insomniac likely......Never did THAT before! Also had the washer fluid hose routing update done. Looks like the vehicle will need some reprogramming/recoding tomorrow to get everything back in line. These items were "fixed" prior to my purchase of the vehicle at my request as part of the deal. Er, perhaps not. The bill is going to the dealer on this one!