How to restart engine immobiliser after disconnecting battery?

Fob didn't work so the alarm immobiliser was armed and active when the locksmith opened the car - with predictable results.

Fob still not working - broken or needs new battery. Have you fitted a new battery into the fob?

The alarm immobiliser will probably remain armed until the doors have been locked and then unlocked with the fob.

There is a small chance the system can be fooled into thinking it has been disarmed by disconnecting the battery (overnight if poss) and then with the door open and the ignition key in and turned on, when the battery is reconnected it might be possible to start the engine...

Battery Disconnect or Replacement Problems
Need to hook up alternative power supply

to install the starter you would have disconnected the battery. this action energizers the immobiliser try using a scan tool to reset the immobiliser.

use a scanner to reset the immobiliser in the CPU program. use the original key when you have done that. The immobiliser probably cut in from the dead battery( if you removed it or disconnected the earth wire then that will do the trick of operation the immobiliser)

If it is not a new key fob, it sounds to me like the immobilizer is activated. So, all the lights on the dash are working now? Is there a flashing key on the dash lights? One of the resets that works is put the key fob in, and turn ignition on without starting it, and leave it 15 minutes. And try again.

try replacing the crank angle sensor located at the front of the engine under the timing pulleys

try using a scan tool to reset the ECM
having a battery disconnect for any length of time can corrupt the CPU program in the ECM

does it have antitheft ?if so u will need to pull fuse for this with battery disconnected then reinstall fuse

Sounds like an issue with the car's immobiliser. In order to prevent theft by disconnecting the alarm system when the power is cut the immobiliser is programmed to interrupt the car restart when power resumed. You will need to reset the alarm code.

disconnect the battery, behind the glove box is a white 4 pin socket, disconnect this, then turn key in ignition to the point just before ignition, reconnect the battery, then turn ignition on, engine should fire, the only problem is you will have to repeat each time you start, best way is to put an immobiliser switch in between the gegative battery terminal and set it on or under the dash, hope this helps