My es300 is not starting - it appears to be immobiliser problem - i have tried both the keys - it has a 1 month old battery and all inside electricals are working ok

This light usually refers to the vehicle's Immobiliser System. Has this light just started to come on recently? Some Nissan models normally have this light flash when you walk away from the vehicle to show that the Immobiliser is active and working correctly while you are away from the vehicle.
If this light stays on when you try to start the vehicle it usually means the security system (the immobiliser) isn't recognising the key you are using. Are you having problems starting the vehicle?
If this is something it has just started doing try this simple fix first. Change the battery in the key fob for a good quality new one. An old battery can sometimes give a weak signal which the security system cannot read correctly and assumes it's an attempt to steal the vehicle.
Is the vehicle's battery in good condition and fully charged? Have you disconnected the battery recently? Some immobiliser systems need to be reset if the battery is removed for long periods.

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)

check that the key is in program with the immobiliser after the battery change

might need the body control reset.

The mechanic that you talked to was exactly right

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/sean_54c3a3dc48a7773c

Immobilizer system can be disarmed using 4 digit code from vehicle security card as detailed in owners handbook.

1-insert and remove key from ignition two times

2-close and open driver door two times

3-insert and remove key once from ign.

4-close and open drvr door twice

5-insert key into ign.,then close driver door

6-turn key to on (not start) then off, twice this is rewrite mode,have all remotes to reprogram it will clear any lost remotes.

7-remove key from ignition,the door locks should cycle twice.if not start over.it may take a few tries.

8-press lock/unlock together and hold for a second

9-release,and press lock on remote,the door locks will cycle confirming program.continue to do other remotes you have,steps 8 and 9.if only one in possession,you are done. To end mode open door or insert key into ignition.

You'll need to follow the steps with no more than a 1-2 second delay between each step.. hope it works

If im not mistaken,your car should have an alarm reset/override.Below the steering column,on the dash should be a slot where you put your remote transmitter to deactivate the alarm.If that works,you then need to have your remote checked and coded by a vw dealer.Good luck.

Check the following....

1) If battery is older than 5 years replace it. Costco sells great batteries if you are a member.
2) Replace the distributor cap, rotor, spark plug wires, and spark plugs if these are more than 60,000 miles old.

Altogether about $100 in parts if you do it yourself.

just unplug the immobiliser unit. its behind the glove compartment for rhd models.