Siluro

If that is the O2 sensor on the far right i would say the cat section has been replaced with decat.

If I was you I would take the car to a Subaru specialist if any your way and get it done and check for any other exhaust parts that are almost dead. Judging by what you found already there maybe more. At the moment your getting nowhere fast. They would do the exhaust and be able to map it if needed. Scoobyworld for example do away with one Cat and say it is MOT friendly (I just mapped mine standard, was going to do scoobyworld, still got and extra 90 ft-lbs). They map it and the extra bhp is noticeable and is worth it. If you are trying to do it on the cheap then maybe not. Could be cheaper in the long run this way. I posted a link from Scoobyparts that should work with no cat and the advert says MOT/Map friendly. Give them a call or is that a bit too pricey? Do not use any cheap copies of parts, always OEM or good aftermarket or it will become really expensive.

Wow that is a nice looking example. Do not think I have seen I Hawkeye Wagon in the UK. Your right there will not be many like that but you will be surprised.

Oh jesus i missed your last post somehow neilt1978. He THINKS its the alternator. You have a parts replacer there by the sounds of it. Now I know why Mr B went off on one.

I wish Mr B was my local Subaru mechanic sounds like very safe hands to me. If you have been replacing bits for this problem then I would consider a new mechanic as they are not doing very well. Buy yourself a multi meter and save yourself some money. I wish I had the space and tools to do all my own stuff. Plenty of resources online.

Also as MR B rightly points out a bad connection going high resistance could cause this and a fire.

I would start with battery and get that tested If all is new. What volts is it at now? Need to get it properly tested though. Sounds like a car thing not a Subaru quirk.

I did not realise alarms chirped at low voltage, makes sense. Either the battery is bad (doubtful), completely wrong rated battery (cold cranking amps) or is being drained as Mr B suggests or the starter motor is drawing too many apps. I had a Fiat Punto that would not start after being left from warm for 4 hours. Fiat could not solve it nor could an independant garage. It turned out to be starter motor which I proved by doing the same test. Since new starter fitted car was fine. I read so many stories of this issue on fiat forums where Fiat had actually changed the injectors and all sorts, sensors etc.. One Poor guy spent thousands and all he needed was a refurb £80 starter motor. The starter motor was drawing too many amps when at a certain temp which made the ECU freak out and not start till the >4th attempt (stone cold car would start first go). I believe the heat soak from the engine would twist the body of the starter as the end not attached to engine would cool quicker and make it work too hard (my theory anyway). Electronics can be an bugger at times and most mechanics are mechanics not electricians. To test starter motor a garage could check the amp draw with a meter if it too high I would suspect the starter. You can look up the proper amp draw for the starter motor somewhere online.

Ooooh I fancy that. Think hawkeye maybe different not sure. Hawkeye typically a 2.5 litre flat.

It still could be just the alarm. If the battery is new then based on my theory it could be the starter motor on way out as that would also drop the voltage if it pulling to many amps. All guess work. The test would just tell you that the alarm is freaking out but not if it was the battery or the starter motor. Again did you by the right rated battery?

Just a point what's the rest like. It is xmas and as a bundle it may work out cheaper in the long run. I do feel for you mate. Not the best start to Subaru life.

Like i said i am just guessing but easy to eliminate with a simple test.

https://scoobyparts.com/subaru-impreza-wrx-sti-exhausts/exhausts-for-impreza-wrx-sti-01-05/hayward-and-scott-2-5-inch-cat-pipe-new-age-impreza Think this is the right bit like your post earlier, this also says MOT friendly and implies it does not require a map. Someone with better knowledge must be able to help you. I feel like it is a bit like the blind leading the blind today. lol.

Ok at least I have caught up now. No I can not find one easily either.

I thought the part with the cat in was bad as well. I must of lost the thread somewhere. I cannot see the part you bought having anything to do with the engine light as it is after the sensor. The Cat part might affect it which you now have get, is that right?

What you said it was the other end. I thought you ordered this part already. That would be a better option if fooked though. Center section with resonator/or without much cheaper.

That looks like a decat version to me.

I am not sure but you may be able to get away with a decat pipe there, cheaper. Someone with should be able to advise on this and if you did decat this section would you need a map?

Based on this diagram that is the front Cat. Bummer.

Which end? Towards the engine or towards the rear of car.

In the colder weather then this would amplify the draw on the battery and making the voltage drop worse. Is it worse when the weather is colder?

I would guess that while starting the voltage drop across the alarm is so big it freaks out. Did you replace the battery with one of the same size, cranking power? If you put a smaller one in that might explain it. Easily tested with jump leads, just wire in another battery (as if jump starting) and if the chirp stops then you have a solution, buy a bigger better battery.

Depends on the error, but if it was cause of the holed exhaust it should go out by itself eventually. Same if the garage clears it, it may not come back on instantly, again depends on the code. I changed an exhaust and O2 sensor on my classic sport and it took a few miles for the engine light to go out. I was worried for a while. For example it may need X amount of passes before it will decide to turn light out. Same when light goes on, with some codes it needs to error X times before it will decide to turn light on.

Good luck. I have my fingers crossed for you. Remember the code may not go out instantly. The ECU needs to learn that the code is no longer valid.

Reading through the thread again hot or cold it does if been switched off for more than 5 minutes. Weird. I still cannot really hear it in the video. The part you repeat sounds like I siad more of a hissing sound. Cause you have actually heard it I guess it is easier for you to hear it in the video.