I've forgotten the code for my Accenta 8 alarm.

not a car or truck it is a home alarm by Honeywell
no model number told
8SP400A?????
it needs service, if the main pad is dead. got wet is top cause
or just too old
this manual match up free

https://prod-edam.honeywell.com/content/dam/honeywell-edam/hbt/en-us/documents/manuals-and-guides/user-manuals/IE1-0040-Rev1-engineer%2520pdf.pdf?download=false

Please read the manual. Link attached:
https://www.manualslib.com/manual/1129455/Honeywell-Ade-Accenta-Gen4.html

Try here
http://www.alarm-supplies.com/user%20manuals/optima-accenta%20g3.pdf

Be sure you understand the difference between a master code and the technician code. A master code lets you program other codes (and do some other harmless stuff). The technician code lets you do anything in the panel. If no master code is known you will need to default the panel. Do that by turning off power and disconnecting the battery. Reconnect the battery or plug pack and within 10 seconds enter 971300 on the code pad. That will wipe the eeprom back to factory defaults, and reinstate user 1 as a master code with a value of 1234. Don't even think of doing any of this without an INSTALLER manual. (Not the same thing as the USER manual). Better still, get an alarm tech familiar with DAS or CADDX products to program it for you. Worth every penny. After that you can add/delete users with your own master code using the much simpler User manual. Any code can be set to be a master code (that is you can have more than one master code)

I'm not familiar with accenta plus alarms but if your motion detector is picking you up then your panel is beeping sounds like the motion is programmed incorrectly.

Default code for ade accenta panels is 0123

Hello
Send your Emai Address to me. I've the user manual for your RCA RC 140. I actually do not remember, from which site did I downloaded it. I can't send it to you by this window, as it does not allow me to upload PDF fiels by it. If you send your Email ID, I'll send a copy of it to you by return mail. OK.

Hello
I've the owners (user) manual for your Teac AG-D9260. But I can't send it to you by this window as it does not allow me to upload PDF files by it. I don't remember from which site I've donloaded it. If you send your email address to me by FixYa comment, I'll send a copy of it to you by return mail. OK.

Hello
To cancell the alarm mode is described in it user manual [page 21]. It is very difficult to type thos symbols here by this window. Just follow the manual. It says, press alarm mode button either on its control panel or on the remote control until the display shows 'no alarm mode' indications. If you don't have the manual send your email address to me by FixYa. I'll send a copy of it to you by return mail. OK.

I dont know why you put this under "watches" but I found a Honeywell customer support site at:

http://www.security.honeywell.com/contact/support/index.html