nujeepguy

after reading threads about "which sensor is bad"

moparado

I agree that CPS couldn't be in a worse hard to get spot.
IMO, using a scope is the best way of testing one of those once the pulse specs are obtained.

I tried changing mine when it died a couple years ago.
All the cuss words in the urban dictionary followed by my bad back giving out and at some point said 'F' it.
Gett'n too old to crawl under vehicles for any length of time any more.
Farmed it out to a shop that had a nice HOIST.

But now that i have a 1" cross member drop, i'm hoping there's enough wiggle room to get to it from the top. If there's a next time that is.

Been think'n off and on about buying a decent hoist for my pole barn.

Been also think'n about buying one of those new OLED TVs.
Been also think'n about trading in my '16 F150 and buying a 2018 Raptor.
Been also think'n about re-roofing my leaky pole barn.
Been think'n about new bumpers for my XJ.
But then my old Farmall tractor needs some serious attention with engine sputtering.
On and on.
Priorities, priorities, it never ends.

nujeepguy

got a chicken coop i store junk in,old wrinkled shingles , leaks. finally found metal to cover it. almost went thru b4 i got done..

hey im thinking now a logic probe

logic probes are $10- $20 cheep

moparado

LOL, no chicken coup here!
My pole barn is 50 feet X 80 feet with an industrial concrete floor!
I once estimated i could sardine 35 or more cars in it.

Logic probes have their place but a scope picture is worth a thousand LED blips.

nujeepguy

wow 50x80 huh? mine is 30x50,old with poles every 10 feet.

right on scopes

jordan96xj

I don't know if a probe would be sufficient. Those blips on the scope are happening a lot faster and more frequently then they appear. It is auto triggering and stabilizing the pattern for you. With a lighted probe, it basically will be constantly lit, with a little bit of pulsing in the light. That pattern you are seeing is actually going by about 13-20 times per second. With a probe, I guess you could at least discern that the CPS signal is present, but I don't think you'd be able to know if it was erratic or out of spec (which is a common failure mode).

I was always very curious if those micro scopes would be sufficient to view a CPS waveform, its cool that you provided the shots to confirm that they actually could do it. I bought a larger DSO for this very type of troubleshooting, but I looked long and hard at the tiny scopes wondering if they would be a good alternative. There weren't enough reviews from automotive DIYers (at the time) so I ended deciding to go with the full sized scope (which are so much more affordable than they were even just a couple of years ago). I got a very full featured scope for $350. Way more features than I'll ever know what to do with.

I've only used it on the primary ignition so far, but was definitely worth the admission price. Threw a fuse buddy into the ignition fuse slot, clamped on the amp clamp, and used another channel with normal voltage probes to mark cylinder #1 firing. Almost immediately had a stabilized view of the entire ignition sequence and quickly identified any particular cylinders that were abnormal.

Truth is, I haven't had to use it as much as I had thought I would yet (knock on wood), but it is nice to know its available if things get weird. Mostly I have just tried to practice with it a few times so that I would be able to use it correctly when the time comes. I still have a lot to learn.

nujeepguy

heres the scope.

jordan96xj

That is one scope that I did not come across when I was looking. I see it has standard probe attachments (a good thing, and necessary for taking advantage of accessories). There are some on amazon that are even smaller (sainsmart), and I loved the idea, but the reviews on them were pretty spotty. Most people said they were good for tinkering, and generally cool in concept, but not practical for real use (screen too small, buggy interface, etc).

If we are finally getting to the point where useful scope can be had for around $100 (like you have shown) then I would start to include it as a must have tool (along with a multimeter and obd2 scanner for 96+ Jeeps).

Here are the sainsmart ones I mentioned:

SainSmart Mini DSO203 Handheld Pocket-Sized Digital Storage Oscilloscope 4 Channels, 8MHz Analog Bandwidth,72 MSps Sample Rate
SainSmart
Link: http://a.co/0I39ZqN

nujeepguy

i appreciate your feedback and moparado. im just starting on this,but its clear, on a good running 4.0 they are short duration pulses ap a 5 v pp level. out of curiosity i took ac readings with 4 dvms and got 4 different but close readings. its a compromise since meters are made to read regular ac volts and not pulses. i guess they average them out and come up with a number that may be an ok guide to either ok or not. clearly a "no" reading is bad but it may depend on the meter.
best is to get a reading while the motor is running good, then compare huh?, with the same meter.
i want to get pix of pulses when cranking but not running. need to disable running but dont like messing with it? an ez safe way? just a fuse to pull?

more later, i want to see the cam pulse today. thats the other one that seems to be a question on no start cases.
hopefully pix to follow

edit, got square waves on cam sensor but couldnt sync right and didnt understand them,yet. they were 5 v pp like the crank though. dont know what to expect there except sq waves. not yet!
still learning the scope, slowly...its not like a regular triggered scope.

jordan96xj

I had intended on doing exactly what you mentioned, that is getting screenshots of my cam and cps signals when they are in good working order, so that I could compare if anything ever gets fishy. I tried to find some "known good" waveforms online, but was not yet successful. There are a few pay services that offer known good patterns, but might as well get my own captured. Plus it will help me learn how to use my scope more. Still a bit green on it.

Where knowing the scope pays off is when you are diagnosing a problem on a cold start in the morning, and you have exactly ONE chance to get it captured on screen. Definitely not the time to be figuring the scope out.

Meters do typically sample and average the voltage readings. In various ways, but for the low end meters, just a basic average. So they are pretty worthless for capturing anything high speed like a sensor voltage pattern or the control pulses on fuel injectors (although a test light or noid light will at least let you know that they are being controlled and pulsing). But meters can do slower things like O2 voltage swings.

moparado

Thats what i would do also if no pulse parameters are readily available.
Meters would only indicate if pulses are there and as you say would give an average or rms voltage (depending on the meter) across the pulse train/unit of time.
A meter would be better than guessing though or taking some static measurement.

A meter would have a hard time detecting intermittent occasional missing pulses not to mention rise/fall times and specific pulse amplitudes.

No doubt about it, an Oscope is the way to go.
Thanks for this thread NuJeep, might even pickup one of those cheapies myself.

nujeepguy

theres stuff i dont understand on this scope and im good on regular scopes. got stuff to learn or figure out. the cam signals varied and were hard to lock but at least i could verify they are 5 v pp as the cps are. i saw pulses not synced and square waves slower that i expected.

btw im looking on wires near the pcm.

ive had a $100 bucks in fun already!!

moparado

Not battery powered! Bummer! That woulda been a big plus for working on cars.

What kind of Voltage requirement does that Oscope need?
Should say on the wall wort.
I myself would be leery of jury rigging something up in order to use the car battery for power and instead stick with the wall wort that came with the unit.

Can't make out the control buttons that good from the picture.
What kind of trigger options does it have?

In addition to the buttons, i see a ****.
Does it have a variable threshold trigger option?
Or only automatic?

I also see two BNC connectors one of which you have the probe connected to.
What is the other connector used for?
Dual channel or external triggering?

nujeepguy

oh , good news, its "dso 08

nujeepguy

better pix but you can download