I truly need some advice on what to do with my wife's 850. We only have one key we can find and it locks and unlocks the doors but will not start the car unless the doors have been unlocked with the remote. The remote just decided to stop working and I cannot start the car. I just trip the anti-theft system. Anyone on here have some advice? I am aware of a Volvo part which is a bypass relay for the anti theft is this my solution? Help!!

 

did you try locking and unlocking the driver's door 5x with the key to see if that resets the alarm?

 

Change the battery on the remote yet?

 

I have changed the batteries in the remote. It makes a small chirp when I press the buttons. I tried locking and unlocking the driver door I still set off the alarm when I open the door and obviously won't let the car start. The remote does absolutely nothing. In fact the only lock the key will control is the driver door. All the other doors are unlocked and don't react to the key when locking.
I have ordered a bypass relay which I am hoping will help. Otherwise I really don't know what else to do.

 

If the key can work on the driver side door.
Close all your windows and door.
Lock the door with the key.
Unlock the door with the key.
Then try to start the car.

If it works, then you have to reprogram your remote.

How to program Volvo 850 remote control key fob

 

I have tried everything with the key. Nothing was working. However through research on here and Matt's I pulled the 210/211 relay and jumped the 'E' and 'F' pin slots on the 210 side. I started the car no problem after that. I have ordered a bypass relay which I think effectively does the same thing. Volvo part # 3545333 bypass relay it goes in the 210 slot. Thank you everyone who has replied!! I appreciate this community greatly!

 

I had a similar problem and got the car started on the side of the road by pulling the fuse which runs the power door lock and related systems. In a pinch, that will work as well.

 

The key and the fob do the exact same thing. When you unlock your drivers door with your key it is EXACTLY like disarming the alarm with your remote. If the car does not start its probably not the alarm causing this.

 

On my 96 850 it works that way. The 97 was bought used with just the one key and fob. The 97 key has never worked at disarming the alarm while unlocking the door. Only by getting the door to unlock using the fob then using the key in the ignition you have no problem. I know it is/was strange.
I have a 96 too, and like you say using the key works just as well as the remote.
I have resolved the issue as far as I'm concerned now. Thanks for the advice!

 

2021 Update to Volvo 850 Broken Key Fob > opening door with key triggers Volvo Guard alarm and cannot start car.

Bought a 1994 Volvo 850 in Sweden in 2020 and over the course of a year the key fobs became less responsive. Eventually both stopped working and no amount of changing batteries and key expert visits worked. There are fewer and fewer people around who know how these old systems work. Couldn't start or move the car.

Based on Vikingleaders post, we ordered Volvo part # 3545333 - bypass relay - removed the Volvo Gard relay and installed the purple 3545333 plug in place of the 210 segment and it worked right away! It's a little bit fiddly but relatively easy

I'd suggest anyone having this problem to try this sollution. The part costs about 30 euros online and should be a first step before going to a car mechanic who will charge to look at it.