Hello from a new member! I will try to outline an issue on my dad's 2008 XC70, which has a chronic issue with the central locking, as in it's been going on for like 2 years. He always took very good care of it which shows in how well it drives and looks, always taken to the local dealer in Kingston ON, as attested by the eye-watering bills in the file he kept. Sadly he died, and his car has fallen to me to sort out and either keep or sell it for his estate affairs.

The issue is with the flaky central locking / key fob operation which even the dealer couldn't sort out, after keeping it for 3 weeks!

In short the fob wont open the doors/unlock/disengage the alarm at all, if the car has sat for more than 1.5-2 hours...you can unlock it with the valet key, and then the fob works fine, as in you can hit the unlock button and the car operates as normal, alarm is disengaged etc. If you then lock it with the fob it works fine for that too; and if you return to use it before too long (maybe 60-90mins) it will also work as normal...but any longer than that, you get nada from the fob, and have to use the valet key again. The battery in the fob is new, and the dealer tried a bunch of things and then just shrugged.

Here's what makes it even weirder...if when locked and the fob is not working, I discovered today that if you pull the tailgate latch above the license plate as if to open it, then push the unlock on the fob, the fob's normal function comes back to life, no need for the valet key!?! This only works from the tailgate latch, it doesnt work if you lift a door handle, on any other door. Extra bit of info is that the tailgate electric lift buttons in the car and on the fob dont make it raise, it starts to lift but gets stuck before moving much (you can hear it click) and so you have to open it manually only.

I wonder if there's any idea here on what might be the cause of this or even what to look at tailgate area to zero in on a fix.

Any thoughts appreciated!

 

FYI I think I figured it out...it's a conflict with the TPMS radio frequency receiver. Apparently the keyless remote receiver is shared with the TPMS.

All the while the car was being checked for this locking issue it had it's winters on. There are no TPMS senders in those wheels so the TPMS/low air warning is always on. When I put the summers on it took a while to recalibrate but eventually it worked, the dash warning went out and then the locks started working as normal again. Then the other day the 'low air' warning' came back, and also the locking went back on the fritz again. I filled up the tire that needed air, and the warning extinguished, as expected.

Later that day the key fob started working again! I wasnt cluing in to the connection of these events, but on the way home my low air msg. returned because there is probably a nail or something in that tire (it's definitely losing air)...and low and behold the locking system is flaked out again.

I read the remote is supposed to send a WUP (keyfob wakeup protocol) signal that 'wakes up' the receiver system to accept the keyfob's commands, and this is being blocked by this TPMS conflict issue, which is why you can only 'wake it up' by activating the driver door with the valet key or by pulling on the tailgate latch, at least when there is an actual TPMS condition.

So what do you think is the fix for this TPMS/central locking conflict...because after the winters go back on, the locks will certainly go back on the fritz...and new receiver module? a reprogram at the dealer?

 

Wheel sensors with the correct Frequency and part number for the winter tires.

The factory sensors might be $90 each, but there are cheaper aftermarket alternatives - Walmart has a 31302096 listed for $21.95!

https://www.walmart.com/ip/TPMS-Tire...0aAk2kEALw_wcB

 

Thanks for that, but I still need to figure out what to fix with the receiver issue...this should not be happening