This car has come in with an intermittent non start fault. No fault codes stored, but I noticed that it didn't display any RPM speed when cranking in live data. A new crank sensor has been fitted and I've checked the circuit back to the ECU and have scoped the sensors output.

What appears a little odd is the scope pattern. The voltage output fluctuates drastically as shown is this trace captured with the engine running at idle.



Looking at the flywheel (Flexy plate?), it appears to run out of true and I'm assuming that the air gap between the sensor and the rotor varies as the engine rotates. This movement appears to be side to side as though the flexy plate (?) is bent. Has anyone heard of this before?