2009 C70 - Key Remote Stopped Working.

[RepairmanJack]

Didn't see any posts on this specific issue and my general web searches were not very helpful.

I have a 2009 C70m 120k on the odometer. Generally serviced by a local mechanic, but I still do work on it when I can. The newer models are challenging to service, even for someone with basic skills and a good set of tools.

On Friday, I locked my car and went into a store. Coming back out, I found that the door wouldn't unlock. None of the remote features on the key fob worked - no locks, no lights, flashers, trunk, alarm etc. Unlocked the car with the blade key, and as soon as I opened the door, my car alarm went off. Key in the ignition killed the alarm.

I replaced the battery - nothing. I didn't get a "low battery warning" on my dash.
I went to the Volvo dealer and they had me try a Volvo battery - nothing.
Dealer tested my fob and confirmed that it was sending a signal - but had no suggestions as to why the car was not responding.

I did some online searches and found a person or two who said that if you disconnect the battery with the fob in the ignition and let it sit for several hours, it would reset or re-pair with the car.

I tried this a couple times and nothing changed.

I also checked the fuses - at least the fuses I could locate. My manual says that the central locks and alarm are on the same fuse - #57, I think. It also says there's a fuse box under the glove box, but I had no luck finding the access panel for this secondary box - even with the diagram in the manual.

However, if the alarm is working, It's likely that there's not a fuse issue if they share the same circuit.

Presently, I don't want to drive the car much as I have to leave it unlocked or risk setting off the alarm. The dealer will charge me $300 for a new fob and programming, but it's probably not going to fix this if the car is not receiving or recognizing the fob.

Any suggestions?

[Cees Klumper]

This, or at least very similar, has been happening to our 2008 C70. Worst has been complete battery depletion within days of sitting, and mildest the car not wanting to unlock or lock with the fob. Same as your situation: nothing apparently wromg with key fob/battery. Recently had to get it towed to Volvo who diagnosed the cause as loose battery cables at the engine/body. After they corrected that it has improved, although still have the 'can't lock with keyfob' issue sometimes. No codes on Topdon Phoenix semi-professional scanner. Another issue that this car has had for years is the auto-start barely works, sometimes you have to initiate the starting up to 6 or 7 times before it will fire up. Volvo was unable to diagnose this. I have replaced the alarm module once which has helped the battery depletion some. The PO had the engine replaced in 2018 due to overheating, I think this may have something to do with the electrical gremlins.