New Aux/12v Battery Results in Alarm!

I have a gen 2 Prius with an auxillary battery that died whilst away for one week. It had previously died whilst parked for a short time so it was not completely out of the blue. The car is currently missing its locking chamber so there's no key access, only remote smart fog access. This meant I had to break-in with a clothes hanger, whiich was not easy because the only way was to hook a loop around the door handle and pull it open.

I tried trickle charging from the front, but this immediately set off the immobiliser (I presume, since it was an alarm, but different to the regular alarm).

My next and final plan was to replace the aux battery altogether. I did my research, bought one online and eventually switched the batteries after a few complications (such as a battery area almost full of water). However when I did the last part, connecting the positive connections, the alarm started going off and would not stop. It was a different alarm sound to the regular alarm, and different to the alarm sound when I tried trickle charging via connections around the fusebox area. I disconnected the battery immediately, but the alarm continued. I then closed the trunk / boot, and the door I had open and it still continued. I also tried using the smart fob to open / lock the car. At this point I was really panicking, but fortunately after about 10 minutes it stopped! The doors are now locked as well, so I am going to have to break in again.

Can anyone help me at this point as I'm out of ideas. If you have any idea of the answers to these questions I would be massively grateful to you!

• Does it sound like the immobiliser I'm setting off? The sound made when trickle charging was a quite quick start stop sort of sound and the lights were flashing. The sound today when I connected the new battery was an continuous alarm sound with short intermitant breaks.

• How did the alarm continue for around 10 minutes with no power source?

• How can I get past the cause of the above? Aside from having another go at plugging it in and hoping for a different outcome (after breaking in that is), I don't know what to try next. The one small thing that I'm kicking myself for not doing now, is getting in the driver's seat when the alarm was going off and putting the smart fob into the 'smart fob hole' (the actualy name eludes me), to see if that sorted it out. Beyond repeating the process just to try this, I don't know what to do.

Thanks ! : - )

 

Hi Bisco, I've only had the car since 2014 so it's a possibility. Any time the alarm has gone off in the past it has always consistently been the same sound (as well as the horn going too alongside it) so I would imagine that means it would be less likely.

Anyone know where this would normally be installed?

 

It could be - fortunately it only lasted 10 minutes, I would have thought it could handle more usage than that.

I will have a look for an after market alarm, but I would be really surprised if there was because I've done enough around the car that I should have come across it really. Is this the only explanation for a 3rd type of alarm sound?

I read another thread where on a 2nd attempt the alarm was turned off by repeatedly using the smart fob to lock / unlock the car. I was trying this when it happened but I can't say I tried more than a couple of times, and then maybe again a few mins later. It's also worth noting that for this person putting it into the ignition slot did not help stop the alarm.

When it happened, because I'd removed the clip style connections from the positive terminal and the alarm continued, it simply doesn't make sense unless there is an alarm (whether original or aftersale) that is drawing power from it's own source.. or even the hybrid battery. to me there is no other way the alarm could have continued. Does that sound right to you guys?

 

Thanks for the reply I suppose it's a possibility.

It must be caused by a leak in the bodywork of some kind. The water was full to the top of the battery 'wing/well', and I can see as more water had come in, it had been then overflowing to the spare tire area. As I've had the car for almost 4 years, only recently discovered the situation, and live in the rainy UK, I would have thought it would not have taken till now for any water damage to occur. It also happened after the car was left unused on my drive for about 10 days.

 

Wow, thank you dolj! What a comprehensive reply! It's great to have some answers to some of the more puzzling parts of all this.

I will give this a go, and let you know how it went!

 

So I finally got in the car yesterday to try the suggestions and it worked! Worth noting to anyone in the same situation that the alarm didn't stop while the key was in the key slot, but did after taking it out of the key slot and pressing lock / unlock several times. I took the car on a drive and everything was working perfect!

But like some cruel joke, that's a little funny, but wasn't at the time, that all changed this morning. I got in the car, tried to power on, and nothing happened. Because I was rushing to leave, I gave up pretty fast and got out the car, which is when it got really weird. I shut the door, tried to remote lock the car which didn't work as expected by that point, but as I turned to walk away the car came on stereo playing and everything. So I got back in and put the key in the slot to try and go, and it turned off and was dead as before. I then repeated this again and again and it repeatedly happened. Eventually on about the 10th attempt to leave without the car turning itself on (I obviously don't want it running all day on the drive), I managed to leave with it remaining off. I couldn't lock the doors, but that's the least of my concerns now.

Anyone ever experienced a Prius that won't start, but starts itself when you exit the car and close the door?

Thanks again

 

Thanks bisco - dolj seems to be the oracle so I have no doubt if he returns!

The latest is I got home from work yesterday and it worked fine! Got up early in the morning to make sure and it was still working fine. When I was leaving though there were some errors meaning I turned it off and on a couple of times. Eventually it worked and I've driven it to work (perhaps foolishly). On one of the times I turned it off and on it was acting entirely dead, no reaction to the smart fob at all, no remote locking unlocking etc.

After getting to work, which went fine, I turned it off, got out of the car and it wouldn't remote lock! So I've had to leave it open. Before leaving I got back in and tried to start the car and it was acting completely dead again!

 

--- ignore this, I thought I could delete the post --

 

Hi dolj,

When I first got the car working correctly and stopped the alarm triggered, it occurred approx one or two seconds after removing the fob from the key slot and pressing lock / unlock. I immediately put the fob back in the key slot and put the car in READY mode. From this point the car drove and operated completely normally.

All connections to the 12v were checked. I also went into maintenance mode on the dash screen two times to check the battery health, and both times it fell within the correct range.

I will have yet another look at the battery connections, but I'm assuming it's not this since I'd checked it all previously.

Thanks!

 

Hi guys,

I believe I now have my situation sorted out. It appears that when putting all parts of the boot/trunk back together the positive terminal connection was partly knocked off, which is quite incredible as it was tightened up a lot.

I've now re-placed it on the terminal, tightened to the absolute maximum I can do with my human hands, and then extremely carefully put the cover parts back in place. Since doing this everything has been working as it should.

I'm very happy to have a working car! It was getting very inconvenient not having it! I'm still at a bit of a loss about some of the things I experienced, for example the car repeatedly starting when I'd left the vehicle and closed the door, but not when getting back in and inserting the smart fob in the key slot.

Thank you very much to those who lended a more experienced hand - especially bisco and dolj!