As mentioned before you can buy a used alarm main unit and plug it in and program your fobs to it and set a new pin code for it if so wished. Only plus with that is remote locking be functional again . Downside is you still dealing with 20 year old european electronics and as it basically can leave you stranded it best pulled out and binned as saves same issue twice (siren board corroded/faulty by leaking P9 battery being super common). I done repairs both ways for customers (option tended to be driven by their preference on alarm and locking). you can add a remote locking system if pull alarm but that adds cost . A working M30 used module is cheapest fix with everything same as owners already use to . You can find used M30 modules pulled from Subarus for around 80 to 150 quid, it must come with pin or a working keypad ( I like a keypad with it as then you got a third keypad that can be used for parts in your key should one of yours fail and it generally easier programming using an existing remote than using pin code) . You got options and none are technically difficult or needs specialist equipment thus the cost to resolve it either way is not crazy money . If you half competent and can google info you could swap alarm module or even bypass it to get running as it really nothing more than cutting and joining some wires ...

Mr B, many thanks for response. An auto electrician (via email) has advised removing unit and a helpful call from Subaru Replacement Key Services seems to confirm alarm unit ECU is dead ?? >> >>No LED in dash, no light flashes on keypad when inputting digits before key inserted. When key inserted the keypad light flashes several times on each digit entry. Alarm DEFINITELY working. its loud and annoys neighbours and puts me off trying to do anything. If I can get a replacement unit is it an easy swap out ? I dont possess a multimeter but inexpensive. Im not overly technical, or experienced. If replacement failed, Id go to a bypass route and sacrifice remote central locking. Currently only the drivers door is locked by key… As immobiliser system appears completely unresponsive but alarm sounds what would you recommend next? Thanks

Reality is it not that big an issue overcome one way or the other . Options are disabling the sigma m30 and bypassing immobiliser circuits (rejoining wires the 2 immobiliser circuits spliced into) . Trying to get the current Sigma working to some functional extent again or replacing the modules with known working used ones (needs be supplied with pin code and/or working fob allow easy programming). No need be a specialist in Subaru as this System is basically added after production line assembly and Sigma systems used on many vehicles in that era including a lot of euro cars . Basically any fairly competent auto electrician, alarm installer or decent mechanic can do this work as it nothing fancy and all you really need is a brain and a multimeter, wiring info is helpful but not a must . What I would do is do few basic things see if can get alarm to function, main thing that goes bad is the siren that located under the wiper plastic trim and sits in the cowl space, this has a P9 rechargable battery inside and they go bad and leak and decay the siren board causing various alarm function issues, just unplug the wire that goes to this siren and test alarm, Also test alarm by having ignition key on and pressing fob button and see if that turns immobilser off ! if does alarm may start function normally again if lucky . You can leave siren unplugged and only issue is you get no siren tones but all will function if rest of system good . If system seems totally unresponsive simplest option is bypassing the Sigma alarm and that pretty quick job to do, only downside is loose the remote central locking as sigma alarm install removed the factory subaru remote locking . The Sigma alarms are nothing but potential problems at 20 years old as it euro made crap, all the Subaru Japan electrics and electronics will be fine and they all independant of the Sigma (besides remote locking) . Even with the Sigma bypassed you still got the Subaru factory transponder key chip immobiliser and that good enough on an old basic Forester . Modern car thieves be lost at trying deal with a car with a physical key and a mechanical handbrake lol . M30 document attached which might be helpful and does include info on pin code use. changing pin code and programming remotes . m30.pdf

Hello, Last week had a new turbo fitted to my 2015 Outback 2.0L diesel, and one exhaust temperature sensor. Love the car. 24 hours later, the second exhaust temperature sensor went with the P2033 error. Checked it with my OBD reader. Took it to Halfords as they said if it is that problem they have the parts, but they would need to do a scan. They scanned, confirmed the error and have quoted me an eye water £607.05 for the sensor. The sensor part no. is 22629AA070, but I can't seem to find one. Does anyone know where I can buy Subaru original/Denso exhaust temperature sensor part?

Thanks again Frank, your post really helped - I updated my maps recently to the November 2025 release without any issues👍