I am having trouble starting a Toyota Yaris with a 2NZ-FE engine. The crankshaft position sensor gives a good waveform (PicoScope) but the camshaft position sensor I get only a straight line. The sensor is a 2 wire inductive. I purchased a new OEM sensor but I still get the same straight line.
It does not seem as if I can adjust the air gap on the camshaft position sensor, but for future reference can anyone tell me what a good gap should be. On the net most images have a gap of 0.5mm to 1.5mm.
Sounds like an open or short in the circuit. With this type of sensor the closer to the trigger wheel the stronger the pulse the main consideration is getting gap as small as possible without running risk of the trigger wheel rubbing on the sensor 0.5 to 1.5 mm is fairly typical.
The rough and ready method is to use the thickness of a business card as a thickness gauge and turn the engine by hand to check it isn't rubbing
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
You may want to scope the sensor while it is disconnected and the engine running or cranking. It will tell wether the problem is on the sensor/trigger wheel side or further upstream.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Not trying to derail your thread about sensor air gap, but... Is it possible you're getting a flat signal line because the camshaft reluctor isn't turning?
Thank you guys for your input. The old camshaft sensor is definitely toast. I removed the tappet cover and checked the reluctor ring. All three "dowel" pins are there. The air gap on the new sensor (which turned out NOT to be OEM) I measured was almost 2.1mm. So I filed down the plastic housing to make it sit closer to the "dowel" pins on the camshaft.
Now at least I get a nice waveform, but the voltage on the Pico (peak to peak) is only 1.453v. This does not seem to make the ECU happy as it is still not starting.
The air gap now is 0.80mm. I can try and file it down some more. As far as I know 1.453v should be enough?
To measure peak to peak voltage you would have to connect the signal lead of one channel to one sensor pin and the ground lead of that same channel to the second sensor pin. If you're using a scope with common ground to all the channels you then can NOT connect a second channel simultaneously to the crank sensor signal and this channel's ground lead to battery negative or chassis ground.. If you did so you would create a ground loop that may keep the engine from starting.
Another important point is to make sure that the cam sensor wires are not switched/inverted and that they enter into the correct pcm terminals. Some cars will not start with inverted signals.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Topic Author
