Never heard of an "ignition sensor". Do you mean oxygen sensor, or maybe crank position sensor, or cam position sensor? There is an ignition "module" also... The oxygen sensor is on the exhaust manifold. The crank posiiton sensor is on the backside of the block. The cam position is on each head.
The crank sensor is located behind the Harmonic balancer. Try not to break the rubber within the Harmonic balancer when removing or on the safe side replace both the Crank sensor and the Harmonic balancer ( the big pulley on the bottom - most part of the engine.)