key fob 2009 xc70

[dhtomlinson]

Hi there,

I have a 2009 XC70 with 187K miles. The key fob will not lock/unlock the door. I switched out the battery, and that is not the issue. I disconnected the car battery, negative terminal. That immediately fixed the problem, and the fob was working perfectly. As soon as I drove the car, the lock/unlock stopped working again.

Any suggestions as to what it might be?

Thanks

Dave

[pgill]

Dave,

I am going to rewrite what you are experiencing. If anything I write isn’t accurate please reply with the corrected information

Problem statement:
The communication between the key fob and the vehicle is not working correctly. By removing the battery cables and allowing the vehicle electronics to go to zero voltage and then reconnecting (a hard reset) the communication is restored. However if I start the car with the Voltage Dip that is expected the communication is broken again.

Based on this information I suspect that the Voltage Dip when starting is too low and therefore the electronics responsible for key fob communication become latched up and stop working.

You can check the voltage at the battery when cranking.

Here is a link with data for a LR2 with the same 3.2 engine

https://www.freel2.com/forum/topic37208 ... oltage+dip

Good luck

Paul

PS if you are confused about what to do to fix the problem if it was my car I would change the battery