AO Silver Member
Join Date: Apr 2002
Hi Bart'n Ivo.
The Phase sensor is also known as the TDC Sensor ( top dead center ) and keeps track of the combustion cycle. Most common places of fitting this is on the rear end of camshafts, inside the distributor or behind the camshaft sprocket wheel. The latter is the case with the Alfa TS 16v engine. I order to change it, you have to remove the timing belt, and camshaft sprocket wheel, minimum 3 hours of work, maybe thats the reason why the workshop hesitated, they could have been short on time.
If the Sensor is located in the distributor, it sometimes require a complete unit (ie. Honda), and sometimes the sensor only, can be replaced.
There are two types of sensors, the Hall sensor and the magnetic inductive sensor. Both of them using magnetic input. The Hall sensor is an electronic device, requiring power supply in order to work. Wheras the inductive sensor generates current when the the teeth of a tonewheel is passing by. A missing tooth then signals the TDC.
I reckon the phase sensor has no direct influence on the power output. It's only there to determine the position of the camshaft. This information is crucial when starting the engine, but when the engine is running the ECU keep repeating it's cycles. Even if the sensor goes totally bust, the engine keeps on running. However once stopped it won't start again.
If the Crankshaft sensor (very much like the Phase sensor) is bust, some cars will keep on running, irregular though, whereas other cars won't run at all.
If the Check engine light is on, meaning the ECU encountered a fault ( ie. faulty Phase sensor) it will enter the "limp home" state. Meaning it will try to preserve the engine by adding extra fuel and delay the ignition = less power.
Hope this Helps