Key fob/alarm locks but doesn't unlock in cold weather

[ActionA]

Hi all, 

I have a very strange issue with my 2009 5-door Yaris. During a very cold winter, my key fob started acting up. It would lock the car on every attempt, but wouldn't unlock it. Sometimes, it could take up to 10 minutes of trying to unlock the car with the key fob. Using the key itself doesn't help in these situations, since the alarm gets engaged whenever I lock the car with the fob and I'm unable to disengage it since unlocking does not work.

Once summer arrived and the weather got warm, the issue disappeared. Now as the temperature is dropping below 15 °C (around 60 °F), the problem is back. 

I already changed the Battery in the key fob, tried reprogramming the key fob and checked all the fuses. The red light on the key fob lights up on both unlock and lock, so the issue must be on the car's side.

I'm starting to think this could be an electrical issue and a bad contact somewhere? The car has a Defa 800-M High-speed alarm installed from the factory. 

Does anyone have any idea what else could be causing this?

Thanks!

[Cyker]

It is quite common for the buttons to break off from their solder points so they're only held in by the rubber thing that presses it - Relatively easy to fix if you have even basic soldering skills. It may also be the buttons themselves have some corrosion, but that's less common.

People sell kits and/or repair services on eBay for such things it's so common.

 

[ActionA]

51 minutes ago, Cyker said:

It is quite common for the buttons to break off from their solder points so they're only held in by the rubber thing that presses it - Relatively easy to fix if you have even basic soldering skills. It may also be the buttons themselves have some corrosion, but that's less common.

People sell kits and/or repair services on eBay for such things it's so common.

 

Thanks! I'm quite certain issues with the key fob buttons are ruled out. The key fob red light lights up for each press, lock or unlock, it's just that the unlock doesn't do anything. I also took apart the keyfob to check the buttons and soldering underneath and everything looked in order.

One small detail: when I'm actually able to unlock the car and the alarm was triggered before, the right turn signals and park lights and left park lights (but not turn signal lights) blink for about 30 seconds. Otherwise all these lights work, so this could be an error code of some sort? I haven't found anything about this in the car or Defa manual. Complete mystery.

[Mooly]

Many years ago now I had a weird issue with the central locking on our old 2003 Corolla. It would lock/unlock fine on the drive but travel a half a mile and it would not lock from the key without a lot attempts and door opening closing. Tried the other key and just the same. 

This went on for many weeks until I decided to have a quick look and more in hope than expectation I squirted the latch mechanism in all the the doors (just from the outside) with WD40. There seemed to be a microswitch visible from what I remember. Anyhow, a good squirt with the straw into all the latches on all the doors and also a bit into the key hole on the drivers door.

It has never had the issue since and that must be 7 yrs or so ago. Still have the car. Strange but true.

[Cyker]

Another thing that might be worth checking is the 12v Battery in the car; When they start to get bit marginal weird behaviours start happening, esp. if it does it first thing but is fine right after you've been driving.

[MikeSh]

38 minutes ago, Mooly said:

This went on for many weeks

If it was winter time it was probably water in the mechanism getting frozen by the wind when travelling.

[Mooly]

14 hours ago, Cyker said:

Another thing that might be worth checking is the 12v battery in the car

Me or the op? 

I remember more now... it was like when you have not shut a door properly. You press lock and nothing at all happened. The WD was an instant fix.

Battery last replaced in 2013 EEK but it still churns it over like a good 'un.  

 

13 hours ago, MikeSh said:

If it was winter time it was probably water in the mechanism getting frozen by the wind when travelling.

It wasn't tbh but its good thinking. I'm sure (absolutely convinced) it was related to something in the drivers door latch sticking and fooling the central locking ECU into thinking the door was still ajar.

[Cyker]

More the Op but is always worth checking when weird inexplicable things happen!

I'm not 100% sure about the Auris off the top of my head but on most Toyotas the door sensor is in the B-pillar and is a little rubber-covered push switch - These can get a bit iffy over time if the rubber splits and guck gets into the switch, but you can 'fix' them by pushing the switch in and out repeatedly as it seems to self-clean to a certain extent?