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Hi im a bit confused with the waveform im seeing...
So upon putting my verus scope on the crank signal wire with the car running im getting a waveform that i cant work out, im getting a fault code for a cam sensor fault but when iv scoped the cam sensor everything is as it should be a nice square wave from 5v to 0v but when iv scoped the crank sensor its a 3 wire sensor and like i say the waveform is wierd. Iv attached some pics of the crank waveform.
I dunno, that looks like a decent crank signal to me? :huh: Is this off your VW Fox? I won't be able to find a known good to compare to, since the US market never got the 1.2L engine. But at first glance, that appears to be a fairly typical Hall effect waveform with a sync notch.
Yh its off the vw fox 1.2, its strange because its giving a cam sensor fault an intermittent one and iv scoped the cam sensor and the form is bang on with the its a nice square wave on and off from 5v to 0v and the ground is good and the power and i cant for the life of me get it to act up, iv tried scoping from a cold start when its not been started for a day, iv tried getting the car hot, iv tried turning it on and off loads of times.
Although check out the cam waveform is this bad? Because when i have been on the freeze frame data for the cam fault the rpm shows 256rpm and iv just noticed now on the cam waveform as i started the car theres some noise in the wave form iv attached the pics for the first few frames as i started it, the yellow is the cam signal and the green is the cam power wire
Can you Post an AC Ripple pattern photo? Check any(all) other 5v feed outputs from the PCM and see if that noise is there. I'm thinking too much AC Ripple, Power and grounds to pcm, and pcm 5 v regulator.
An AC Ripple test should be done at the alternator's B-Post as the battery can absorb or buffer the ripple.
Hook up a lead from one of your scope channels to the B-Post on the back of the alternator, if access is to hard you can go directly to the positive terminal of the battery, just keep in mind the ripple might be reduced, though if its bad enough to cause problems you should be able to see it
In the channel probe settings you want to turn on AC Couple which will filter out all DC voltage and only show AC voltage. Remember DC couple still shows AC ripple but only on the very top of the voltage line and usually you can't scale it enough to measure it without AC Coupling the scope.
Cam signal looks good, the little bit of noise you see if perfectly fine.
Crank sensor waveform looks OK. I have seen crank sensor waveforms with a slight curve to them and cause no issues. Maybe the sensor is a little sluggish but I wouldn't tread that way just yet.. It is true that some vehicles will set a cam code for a crank sensor and visa-versa
Can you get set you scope to 100ms or 200ms and start recording to capture the cam signal during cranking and at idle. Stop the capture before the buffer starts to overlap. 100ms and 200ms should give you more than enough buffer to hit the stop button. This will tell us if the cam sensor is not picking up the tone ring during cranking. You can then zoom the waveform out to see repetition but you are able to zoom in for detail as well.
Does the code set every single time during cranking?
In your verus software there is a preset for ac-ripple testing, look for it . It will also tell you what this test is actually about.
As others have stated, both sensor waveforms look completely normal .The noise while cranking is probably caused by the high starter current, nothing to worry about.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Another thing I like to do as well when using a scope or doing voltage drops is perform your tests. then perform your tests with a booster cable from BAT GND to the engine block to see if results are different. This has saved my butt more than once lol
Right so iv done a voltage drop test with KOER on the cam power and the cam gnd and iv attached some pics of each of them and also iv done an ac ripple test on the batt gnd to batt + because the alternator post was difficult to get on without pulling things apart and iv attached pics of that, and my other test iv done was the cam signal with the scope set to 100ms and then cranked the car and let it idle so iv also attached them pics.......
So the 0.02v was the voltage drop from sensor gnd to batt gnd
The 9.2v was the voltage drop from sensor power to batt +
More cam signal pics iv showed the zoomed out pics aswell and as you can see the square waves are not perfect squares theres like little tiny spikes all the way along
Yh the pwr for the cam sensor is a 5v pwr feed so ill also redo the voltage drop on that from the sensor pwr to pcm.
So them spikes that are 1/2 a volt what are they telling us? What could be causing them?
There is also a thought in the back of my mind of it being a faulty pcm because it is also throwing codes for the pcm signal and also the same code in the brakes module giving a pcm signal code and a few other random faults in other modules
