The back up power supply is from the car battery but is separate to the main feed its purpose is to keep the ECU 'alive' with the ignition off. Its usually the same fuse as the interior light and the radio, if it is not present then the ECU will have to boot from cold when the ignition switches on, that takes longer than the timeout in the immobiliser and the immobiliser will flag a communications error.
__________________
1984 Suzuki SJ413K pick up, 1.6 16V Baleno engine 2000 Suzuki Vitara 1.6 8V, many mods 2004 Suzuki Ignis 1.5VVT 4Grip 2006 Suzuki Jimny 1.3VVT JLX+ and many more.
Sorry to be a bit dim, when you say back up supply I presume you are referring to something other than the car battery ? If yes where do I look and find it or us it part of the ECU?
Hi there, im trying (what seems like in vain) to get my wifes GV repaired its only done 60k miles so i'm not inclined to bin it yet and don't mind spending a few hundred to get it fixed (obviously the cheaper the better).
the car was left for a few months without being driven, the battery went dead and in between either jumping, removing, and replacing the battery something has happened to the ecu/immobiliser. the immobiliser/key light on the dash flashes. car cranks but will not start.
Had a key code specialist come and he said the keys are all ok and coded its the ecu or immobiliser thats the issue.
what came up on the reader was:
Fault code 23
No ecu code txd
I haven't got the ecu or immobiliser out yet, may leave this to my local garage.
I have a couple of questions.
Can I get an ecu & immobiliser from a breakers yard (from the same 1.6 petrol 2004 vehicle) with keys and swap it over?
Does it matter if the ecu is from a manual vehicle (mine is auto)?
Or
Remove damaged ecu/immobilser and send off with keys to a ecu repair specialist ?