Keyless remote won't work after car battery died

jippyt · Post by **jippyt** » Wed Jul 26, 2017 9:58 am

Jumped the car after battery was dead. Now keyless remote fobs will not work to unlock/lock the car. Help is greatly appreciated.

Post by **yagger** » Wed Jul 26, 2017 4:55 pm

Try to disconnect one more time.

jippyt · Post by **jippyt** » Thu Jul 27, 2017 4:15 am

Disconnect? I am not sure how to do that. I do greatly appreciate the assistance.

Post by **yagger** » Thu Jul 27, 2017 3:23 pm

You must understand and remember that you are performing all operations at your own peril and risk. If you are not sure, better, let experts do it. I am not responsible for any damage that you can cause your car, your own or anyone's health, to do it by your actions!

Usually the battery disconnect procedure is as follows:
You need to remove the key from the ignition, wait 5 minutes, disconnect the negative wire from the battery.
Connection:
Insert the ignition key and turn it to position 2, connect the negative terminal to the battery. During the connection of the battery in the car's cabin there should be no people!!!

jippyt · Post by **jippyt** » Sun Jul 30, 2017 9:23 am

Thanks. It worked. Also, found this online to give some of the background on the procedure:

You would think this is simple right? Well, I have heard several people in online forums messing up their Electronic Climate Control while doing this simple procedure. With all the hidden electronics logic which we can not visualize, it is a bit of mystery how this occurs to me. The best I can imagine is if ECC is "on" somehow while you dis/reconnect your battery, it might be the cause of this.

Before you say "But my key is out!" The ECC actually has a temperature fan that remains running for a few min after the key is out. So waiting for a period of time before disconnecting the battery is Volvo's procedure for doing this. Furthermore, Volvo's procedure for reconnecting the battery is to have the key turned to position II (accessory on, headlights on). So I always turn everything off on the ECC before shutting the car down (AC off, fan off, not in automatic temperature mode) when I plan to disconnect the battery. I figure when I reconnect the battery, it is best if the ECC doesn't surge to all of its functions on right away while the battery terminal connection pulses the system with rapid power on/offs.

Well, first, the battery is in the back and requires removing a couple of covers and brackets. The following sequence is what Volvo specifies whenever you dis/reconnect battery

Turn everything off. Radio, All ECC functions to off (fan speed, AC etc, heated seats etc...)
Wait 5+ min after key is out to make sure everything in the car is off. I turn everything on the ECC is off for safe measures (AC, fan..)
Disconnect negative terminal
When you are ready to reconnect the battery, do this.
Insert key and switch to position II
Reconnect negative terminal
Turn the key to off
Lock and unlock door (reset upper cabin electronics, without this step, your sunroof/homelink may not work)
Now set your clock
When the battery is connected, the headlights and various electronics will power on instantly. This feels weird compared to most cars but it is the proper procedure on this car according to the factory service manual.

An example procedure is here

http://www.volvoxc.com/resources/how-to ... emoval.pdf

When I have read people frying their ECC after dis/reconnecting battery. I'm guessing they might not have followed this sequence to a T. ECC is actually still operating for a little while even after shutting down the car and keys out. Maybe they left the AC or fan on that caused this problem. There is probably no way to know unless you get to understand the ECC software + electronics inside.

Sometimes, after battery dis/reconnect, some of your upper cabin electronics (sunroof, homelink, dome light near the rear view mirror) may not work. I hear this is due to electronics subsystems that didn't reinitialize properly. Just lock and unlock your doors with driver door switch or remote. It will initialize properly.

bense · Post by **bense** » Mon Jul 16, 2018 9:51 pm

This fix worked perfectly for me. Thank yoU!

rogreact · Post by **rogreact** » Sun Jul 14, 2019 11:40 pm

Will this work for a 2007 s40 t5 all wheel drive? Sounds like it will but I thought I would ask before I start

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Keyless remote won't work after car battery died Topic is solved

Keyless remote won't work after car battery died

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