The car equipped with the 1.4 8V 350A1000 engine with phase shifter came to the workshop with a shaky idle due to a deterioration of the valve seats caused by the LPG system installed after installation.

The cylinder head is disassembled, overhauled and reassembled, the timing carried out using specific equipment and according to the prescribed procedure, and the work is completed.

On restarting, the engine starts normally but immediately registers the fault 'P0340 phase sensor', which did not occur before the intervention.

Normally this fault occurs due to an error in the ignition timing, so the ignition timing is rechecked but no anomaly is found. The phase sensor wiring and the sensor itself is then checked but everything is in order.

Using an oscilloscope, the phase sensor signal is then sampled together with that of the crankshaft sensor and compared with that of a car that, fortunately in the workshop, had the same motorisation, and a fault is then detected in the square wave of the phase sensor.

Later, after dismantling the tappet cover, damage was found to the gear keyed to the camshaft, which was slightly bent on one of the teeth, thus making it 'invisible' to the phase sensor itself, damage probably caused unintentionally as a result of an impact during grinding.

We proceeded to replace the camshaft and resolved the fault.

I enclose the two screenshots of the oscilloscope, which could certainly be of help to those like me who did not have the correct sample signal to compare, and the picture of the phase gear in order.