Vehicle was running fine.
One day, wife turns on headlamps and horn starts blaring.
Shuts lights off, horn stops.
This is consistent and repeatable.
Went to start it next day and battery is completely dead.
Hooked up jumper cables and got lots of sparks.
Let it charge up a minute and had her turn the key.
Rav started right up.
As soon as I removed jumper cables, the Rav died.
I re-connected cables (again lots of sparks) and the engine started cranking itself – without the key inserted.
Again, this is consistent and repeatable.
There are no blown fuses and the relays seem fine, but I haven’t replaced any.
I have access to an automotive probe and a basic understanding of automotive electrical, but don’t know where to start in this case.
Sounds like the starter relay/solenoid is sticking a bit. Also the Battery is not being charged. The alternator is not charging the battery and or the battery itself is no longer able to take a charge. That is why the engine dies as soon as the jumper cables were removed.
If the battery is around 4 years old or older it would be a good idea to replace it anyway. Once the battery is replaced then you can perform further testing.
You can tap on the starter relay/solenoid with the end of a screw driver and it may cause it to release.
Check all fuses and Fusible links. Here is a wiring diagram for reference.
1997 Toyota Rav4 Charging System Wiring Diagram
