help with component test(s)

[cbender]

I seem to be having issues with component test illustrations. I find it hard to follow along. Alot of times there are no sample waveforms for comparison or the pattern looks nothing like the sample pattern with the pre-configured scope settings.

For instance, the test below tells me the frequency should be 33hz @ Idle. How to I determin this pattern is @ 33hz or do I just not know how to read the scope?

[Crusty]

I seem to be having issues with component test illustrations. I find it hard to follow along. Alot of times there are no sample waveforms for comparison or the pattern looks nothing like the sample pattern with the pre-configured scope settings.

For instance, the test below tells me the frequency should be 33hz @ Idle. How to I determin this pattern is @ 33hz or do I just not know how to read the scope?

From what I can see in the pic, the red numbers on the left are indicating the Hz scale. For the most part, the trace is just above 25 and below 50. Did you "snap" the throttle six times to create the jumps up to 225-?
If you did, the machine is automatically adjusting the scale so it can register the peaks near 225, and so the lower horixontal trace isn't showing a good resolution. Try a slower more gradual application of the throttle and see if the machine stays with a lower scale display, which would show a better example of what appears to be something near the 33Hz indicated.
Try manually adjusting the scale down to about 60Hz so the 33 is about 1/2 way up the scale, and bringing the engine speed up gradually and see if the signal rises gradually up from the base signal of about 33.
I suppose the six spikes up to 225 could be a bad lead connection, if it jiggled quickly enough it may not "drop out", but rather, pick up the speed of the connection jiggle.
I see at the bottom of the screen, you're working on a 99 GM truck. What kind of voltage signal do you get, and how "clean" is that signal??

[Rich Shepherd]

I seem to be having issues with component test illustrations. I find it hard to follow along. Alot of times there are no sample waveforms for comparison or the pattern looks nothing like the sample pattern with the pre-configured scope settings.

For instance, the test below tells me the frequency should be 33hz @ Idle. How to I determin this pattern is @ 33hz or do I just not know how to read the scope?

You can display a digital value for frequency by pressing the Data button at the top or the fingerprint icon at the lower right. Both buttons toggle the graph display area in the bottom half of the screen between all graph, very small graph with digital values, and just the controls for making setting changes.
You can use the meter button on the top to toggle between half screen, full screen, and floating window which allow a better view of just the graph window.
The frequency of the signal will change with idle speed so that is why the text states it will be about 33 Hz.
The spikes in the Hz graph may be from connections as mentioned in another reply or they could be from noise.
Double check the connections and try moving your leads farther away from any plug wires if possible as they are a common source of noise.
If you still see the noise on the Hz graph, you will have to look at waveform in the signature test.

[cbender]

The snapshot is at idle, meter is at default settings for this component test. I do know how to toggle the meter, I just wanted to show the test in the snapshot. There is no sample waveforms for comparison so I am having difficulties deciding if I have a bad ckp due to what the test states.

[Rich Shepherd]

The snapshot is at idle, meter is at default settings for this component test. I do know how to toggle the meter, I just wanted to show the test in the snapshot. There is no sample waveforms for comparison so I am having difficulties deciding if I have a bad ckp due to what the test states.

In this case, the graph would be expected to be a flat line at about 33 based on the information with the test.
Its not conclusive in this case even though it is not flat.
As Crusty indicated, it could just be connections (Scope to vehicle or actual vehicle connections). What happens if you wiggle the connections?
Do you note any change in the vehicle operation when a spike appears on the graph. If you don't, the spikes you observe could be scope connections or noise being picked up by the leads and not an indication of a vehicle problem.
You are probably going to have to look at the actual waveform (signature test) and see how it looks. There should be a sample for comparison in that test.

[cbender]

The truck came in for a no start, which was the ign module. I scanned it and it had a P0338 (CKP Sensor 'A' Signal High Frequency) I did not notice any runnability problems once the module was replaced but wanted to check the CKP sensor. There is a usb for the ckp. Here is the signature test.


I no longer have the vehicle, I put a CKP per tsb but got busy and was not able to scope the new sensor for comparison. The signature test looked ok to my understanding but it stated that the ckp should cycle at about 60% duty cycle and I was wondering exactly how to figure 60% compared to what the scope is showing?

[Crusty]

The truck came in for a no start, which was the ign module. I scanned it and it had a P0338 (CKP Sensor 'A' Signal High Frequency) I did not notice any runnability problems once the module was replaced but wanted to check the CKP sensor. There is a usb for the ckp. Here is the signature test.


I no longer have the vehicle, I put a CKP per tsb but got busy and was not able to scope the new sensor for comparison. The signature test looked ok to my understanding but it stated that the ckp should cycle at about 60% duty cycle and I was wondering exactly how to figure 60% compared to what the scope is showing?

The waveform you show here is nice & clean. Looks OK but that doesn't mean you wasted your effort on the crank sensor. I'd probably think about replacing it anyway, especially when they change the part number to a new updated part.

As for the "duty cyclce", that's the amount of time the waveform is either on or off. If "on" is when the voltage is up, compare that to the length of time it is "OFF" or at 0-volts.
If it was "on" with a 50% duty cycle, both the high voltage time and the low voltage time would be the same.
If it was "on with a 90% duty cycle, the upper voltage would be much longer than the "off" lower voltage of 10% so the low voltage would be much shorter across the screen.
If you can pause the screen, then turn on the cursors and measure the rise and fall of the waveforms, measure the upper voltage time and then measure the lower voltage time, and then you know what the duty cycle actually measured is.
What I see there looks pretty close to a 60% duty cycle.
HTH