X300 engine immobilised

My fob will not unlock my car and the engine will not turn over. After the initial dash lights check on turning the ignition the Check engine light goes out.

I have been told my engine is immobilised and I have to change my Excitor Coil Reader mMdule,

Can anyone tell me more please?

What is my excitor coil reader module and how do I change it?

TIA

Adam 6.0 X300 63K