Oscilloscope...

[richfinn]

Rulers... ugh.... I have a lot to learn

Don't be put off, it can be a bit daunting at first

rulers/cursors are simpy a pair of lines you can move around the screen on a waveform horizontally or vertically to measure a time period or voltage difference

Anybody can learn to use a scope, even me!!!

 

[SuzukiGS750EZ]

I don't see what my owon can handle but it says the Autel is 200v safe (overload protection). You think I need one that can handle up to 400v?

 

[SuzukiGS750EZ]

Don't be put off, it can be a bit daunting at first



rulers/cursors are simpy a pair of lines you can move around the screen on a waveform horizontally or vertically to measure a time period or voltage difference



Anybody can learn to use a scope, even me!!!

You have faith [emoji1787] I'm trying!

 

[2ndGearRubber]

I don't see what my owon can handle but it says the Autel is 200v safe (overload protection). You think I need one that can handle up to 400v?

200 is more than enough. Really 20v input max is fine, if you simply put a 10/1 attenuator on every lead you use to measure voltage. 20v and 10/1 is 200v.

My Pico4425 is 200v max rated input. In theory this should be safe for anything you'd measure in automotive; outside of sticking a lead into the business end of an ignition coil. I still use attenators for primary ignition voltage, and injector voltage. Just for safeties sake and a good habit in case you ever use a scope with a lower limit.

Don't be put off, it can be a bit daunting at first

rulers/cursors are simpy a pair of lines you can move around the screen on a waveform horizontally or vertically to measure a time period or voltage difference

Anybody can learn to use a scope, even me!!!

Everyday is another thing to learn. To think, just a few years ago I saw my first secondary pattern. It's like magic.

Pop a plastic panel off for the fuel pump wiring, take a current ramp. One commutator drops out to zero, average current is 10amps! Power/ground good, bad commutator is the cause of the intermittent stall and crank/no-start. Literally a 5-6min call including printing a wiring diagram. Didn't even need it to act up. Pop the panel, amp clamp, review pattern, sell fuel pump job.

 

[richfinn]

I don't see what my owon can handle but it says the Autel is 200v safe (overload protection). You think I need one that can handle up to 400v?

No , not really

Your looking for the max input voltage in the specs

You can use an attenuator that will increase the max input voltage on that channel by a factor of 10/20 typically

It's mostly when your measuring ignition systems that you need to be careful, even the primary low voltage side can spike above 200v when the coil fires

 

[richfinn]

200 is more than enough. Really 20v input max is fine, if you simply put a 10/1 attenuator on every lead you use to measure voltage. 20v and 10/1 is 200v.

My Pico4425 is 200v max rated input. In theory this should be safe for anything you'd measure in automotive; outside of sticking a lead into the business end of an ignition coil. I still use attenators for primary ignition voltage, and injector voltage. Just for safeties sake and a good habit in case you ever use a scope with a lower limit.





Everyday is another thing to learn. To think, just a few years ago I saw my first secondary pattern. It's like magic.

Pop a plastic panel off for the fuel pump wiring, take a current ramp. One commutator drops out to zero, average current is 10amps! Power/ground good, bad commutator is the cause of the intermittent stall and crank/no-start. Literally a 5-6min call including printing a wiring diagram. Didn't even need it to act up. Pop the panel, amp clamp, review pattern, sell fuel pump job.

The amount of garages I go to and explain this test to is ridiculous

"but it's running, it can't have a bad fuel pump"

Yeah, until it stops on the bad spot right there!!!

 

[SuzukiGS750EZ]

I don't know where to start. I think I'm going to go with the Autel for now to learn on since I have the Scan tool and a I've done with other tools or hobbies, once I narrow down exactly what I need, I'll buy better then. Your wisdom hasn't gone unnoticed though and I appreciate all the input. I'll get a Pico down the road for sure.

What advice do you have as far as diagnostic route learning? I saw and remember can bus signal mirrors itself. How do I know what I'm looking at besides a mirror? What if it's mirroring but a bad signal? When I hook up to a sensor with multiple wires it's ground to ground and what, 5v? Where did you guys learn to read the scope and also understand what it's telling you?

 

[richfinn]

I don't know where to start. I think I'm going to go with the Autel for now to learn on since I have the Scan tool and a I've done with other tools or hobbies, once I narrow down exactly what I need, I'll buy better then. Your wisdom hasn't gone unnoticed though and I appreciate all the input. I'll get a Pico down the road for sure.

What advice do you have as far as diagnostic route learning? I saw and remember can bus signal mirrors itself. How do I know what I'm looking at besides a mirror? What if it's mirroring but a bad signal? When I hook up to a sensor with multiple wires it's ground to ground and what, 5v? Where did you guys learn to read the scope and also understand what it's telling you?

It's well worth investing a good textbook on Automotive Oscilloscope diagnostics (I like James Dillon's from tech topics in the UK)

The PICO website/free software download has lots of waveform tutorials with notes

YouTube can be a good training resource, I think this video answers all you CAN questions, he is a great teacher make sure you subscribe!!!

 

[theoldwizard1]

Underselling their skills IMO. But hey, if you're a customer that's a great value.

UNQUESTIONABLY ! But it is all about the market you are in !

In a high volume market (Ivan live out in the countr, Eric O. in a small town), they could easily get $100/hour, maybe even $200/hour on high end BMWs and Mercedes !

 

[theoldwizard1]

You can copy a signal and inject it into wires?! Basically making a copy of a sensor?

I don't think this would be useful because your "injected signal" was not synchronized with the other data.

Simple case. In the very early days of EFI, you could get and engine to add more fuel and spark if you substituted a fixed resistor for the engine coolant temperature sensor that made the computer think the coolant was <40F. Now a days, the software is smart enough to know that if the inlet air temp is >90F, the coolant can't be that cold. Even if you "fake" both sensors, the software will look at other data (time since start) and figure something is wrong.

You have to remember those engineers have had over 40 years to refine their "strategies". Plus CARB/EPA have been pushing them to detect invalid sensor data. (More than 50% of the software in a PCM is just for monitoring and diagnostics.)

 

[theoldwizard1]

I don't see what my owon can handle but it says the Autel is 200v safe (overload protection). You think I need one that can handle up to 400v?

Use 20x attenuators. The ignition coils and injectors have the biggest "kick" (back EMF) and they are typically clamped to <100V (don't want that kind of voltage back inside the PCM).

 

[theoldwizard1]

To think, just a few years ago I saw my first secondary pattern. It's like magic.

I remember taking a correspondence course back in the early 70s that explained secondary wave patterns (For those of you who don't know, this is what the oscilloscope on the old Sun machine oscilloscopes showed).

The big benefit (especially on the Sun machines) was being able to compare all of the waveforms side by side, and if you knew what you were looking for, detect high voltage breakdown in the coil, cap, wires or plugs. Of course with COP, most of those things do not exist any more. The experts (Scanner Danner) will tell you, all of the data is there even in a primary side trace.

Pop a plastic panel off for the fuel pump wiring, take a current ramp. One commutator drops out to zero, average current is 10amps! Power/ground good, bad commutator is the cause of the intermittent stall and crank/no-start. Literally a 5-6min call including printing a wiring diagram. Didn't even need it to act up. Pop the panel, amp clamp, review pattern, sell fuel pump job.

Need an amp clamp (low current), but you are 100% correct !

A high current amp clamp is a quick way of doing cylinder to cylinder compression. (Any one try the old trick of just wrapping a few turns around the ground cable to detect starting current ? Actual value is not important, it is the relative contribution from each cylinder.)

 

[theoldwizard1]

What advice do you have as far as diagnostic route learning?

Find Scanner Danner's YouTube channel. He is a professional diagnostic instructor.

If you are really serious, buy his book and videos.

 

[richfinn]

Find Scanner Danner's YouTube channel. He is a professional diagnostic instructor.

If you are really serious, buy his book and videos.

Thats a good call

Paul Danner is a really great teacher and helped me a lot when I wanted to improve my diagnostics

The other books are by James Dillon in the UK who runs a tech training business called Tech Topics

 

[SuzukiGS750EZ]

Are these books written in a dumbed down form in the beginning for somebody who doesn't know diagnosis. I mean, I do to a degree, I'm just curious if they expect you have some background. I follow both danners on the tube, he was where I first found out about o-scopes and how in depth it can get. I found diagnose Dan yesterday as well.

 

[richfinn]

Are these books written in a dumbed down form in the beginning for somebody who doesn't know diagnosis. I mean, I do to a degree, I'm just curious if they expect you have some background. I follow both danners on the tube, he was where I first found out about o-scopes and how in depth it can get. I found diagnose Dan yesterday as well.

Thats a good question

They are aimed at experienced vehicle mechanics

I think at oscilloscope level trainers automatically assume you have an understanding of basic auto electrics and wiring diagrams etc.

There is always some mathematics and physics involved

You will be fine!!!

 

[richfinn]

I remember taking a correspondence course back in the early 70s that explained secondary wave patterns (For those of you who don't know, this is what the oscilloscope on the old Sun machine oscilloscopes showed).

The big benefit (especially on the Sun machines) was being able to compare all of the waveforms side by side, and if you knew what you were looking for, detect high voltage breakdown in the coil, cap, wires or plugs. Of course with COP, most of those things do not exist any more. The experts (Scanner Danner) will tell you, all of the data is there even in a primary side trace.


Need an amp clamp (low current), but you are 100% correct !

A high current amp clamp is a quick way of doing cylinder to cylinder compression. (Any one try the old trick of just wrapping a few turns around the ground cable to detect starting current ? Actual value is not important, it is the relative contribution from each cylinder.)

I've not tried that trick, but I do use A/C volts at the battery terminals to do a quick relative contribution test sometimes, it works fairly well if my current probe is not to hand

When I was a teenager we had an old Crypton Tuner in the workshop (British equivalent of Sun or Allentester) this was my first experience of an ignition scope with Raster and Parade display!!!

 

[theoldwizard1]

Are these books written in a dumbed down form in the beginning for somebody who doesn't know diagnosis. I mean, I do to a degree, I'm just curious if they expect you have some background.

The most important thing for electronic diagnostics is a strong background in basic 4 stroke engine principles. Pistons go up and down, crank goes round and round. Fuel, air and spark at proper ratios and at the correct time, plus understanding that the PCM can "adjust" all of those. Experience helps a lot, like being able to detect, by ear/sight, an occasional misfire on a multi-cylinder engine.

Many rookies let diagnostic trouble codes (DTCs) jump to a conclusion. One of the most common is letting a DTC code lead you to replacing and O2 sensor when it is some kind of vacuum leak ("pirate air"). Again, experience helps a lot.

Second is BASIC electricity starting with Ohm's Law !



You must be able to receipt it in all directions and UNDERSTAND how to use it to your advantage.

The next part of basic electricity is inductors (coils) and capacitors. All motors solenoids and even incandescent light bulbs have inductance because they all have a loop of wire. What you need to know is that inductors RESIST CHANGE IN CURRENT ! When you "turn on" an inductor if takes a very small amount of time before it is fully ON. When you turn off an inductor it takes a very small amount of time before it is fully OFF. (Watch an incandescent light bulb. You can actually see this !). Capacitors RESIST CHANGE IN VOLTAGE ! You very rarely see capacitor in automotive circuits.

Last is electricity and magnetism.

When a magnet is passed near/through a loop of wire (which is also an inductor; more in a minute) electricity is created. The amount of electricity (voltage and current) depends on the strength (closeness) of the magnet, how fast it is moving and how many loops of wire.

A loop of wire will create a magnetic "field" when current flows through it. That field can move iron/steel. That is a solenoid/injector/motor. When you turn off the current it is just like passing a magnet near the loop of wire (inductor) as I just mention. This creates electricity going BACKWARD (back EMF).

You have to understand how all of this works in the real world (experience).

You have just completed 1/2 of a first year college physics course !

 

[SuzukiGS750EZ]

This is the scope I currently have. https://www.owon.com.hk/products_owon_vds_series_pc_oscilloscope
VDS3102

 

[SuzukiGS750EZ]

The most important thing for electronic diagnostics is a strong background in basic 4 stroke engine principles. Pistons go up and down, crank goes round and round. Fuel, air and spark at proper ratios and at the correct time, plus understanding that the PCM can "adjust" all of those. Experience helps a lot, like being able to detect, by ear/sight, an occasional misfire on a multi-cylinder engine.



Many rookies let diagnostic trouble codes (DTCs) jump to a conclusion. One of the most common is letting a DTC code lead you to replacing and O2 sensor when it is some kind of vacuum leak ("pirate air"). Again, experience helps a lot.



Second is BASIC electricity starting with Ohm's Law !







You must be able to receipt it in all directions and UNDERSTAND how to use it to your advantage.



The next part of basic electricity is inductors (coils) and capacitors. All motors solenoids and even incandescent light bulbs have inductance because they all have a loop of wire. What you need to know is that inductors RESIST CHANGE IN CURRENT ! When you "turn on" an inductor if takes a very small amount of time before it is fully ON. When you turn off an inductor it takes a very small amount of time before it is fully OFF. (Watch an incandescent light bulb. You can actually see this !). Capacitors RESIST CHANGE IN VOLTAGE ! You very rarely see capacitor in automotive circuits.



Last is electricity and magnetism.



When a magnet is passed near/through a loop of wire (which is also an inductor; more in a minute) electricity is created. The amount of electricity (voltage and current) depends on the strength (closeness) of the magnet, how fast it is moving and how many loops of wire.



A loop of wire will create a magnetic "field" when current flows through it. That field can move iron/steel. That is a solenoid/injector/motor. When you turn off the current it is just like passing a magnet near the loop of wire (inductor) as I just mention. This creates electricity going BACKWARD (back EMF).



You have to understand how all of this works in the real world (experience).



You have just completed 1/2 of a first year college physics course !

Yup. Learned something new today. Thank you!

 

[SuzukiGS750EZ]

This may be an odd question, but what can I do at home to get comfortable with using the scope? I kinda poked this with my meter when I first started learning how to use it, checking voltages, finding grounds. Or even in the car? How can I purposely set a fault so I can see the before and after?

I have the money for a meter but until I learn more or have a practical reason to apply it or "practice", I'm not going to buy it, as much as I want to!

 

[richfinn]

This may be an odd question, but what can I do at home to get comfortable with using the scope? I kinda poked this with my meter when I first started learning how to use it, checking voltages, finding grounds. Or even in the car? How can I purposely set a fault so I can see the before and after?

I have the money for a meter but until I learn more or have a practical reason to apply it or "practice", I'm not going to buy it, as much as I want to!

What kind of vehicle do you have access to??

Do you have wiring diagrams for it?

My suggestion would be pick out a couple of simple sensors and do some data gathering, you need to learn what a good signal looks like to recognise a bad signal

 

[SuzukiGS750EZ]

What kind of vehicle do you have access to??



Do you have wiring diagrams for it?



My suggestion would be pick out a couple of simple sensors and do some data gathering, you need to learn what a good signal looks like to recognise a bad signal

Just go back probing wires? Lol

 

[SuzukiGS750EZ]

What kind of vehicle do you have access to??



Do you have wiring diagrams for it?



My suggestion would be pick out a couple of simple sensors and do some data gathering, you need to learn what a good signal looks like to recognise a bad signal

I drive a 2014 nissan altima

 

[richfinn]

Just go back probing wires? Lol

Wiring diagram!!!

You really need to know which wire is signal/supply/ground

Maybe start with something simple like the 2 wire coolant temp sensor

 

[SuzukiGS750EZ]

Wiring diagram!!!



You really need to know which wire is signal/supply/ground



Maybe start with something simple like the 2 wire coolant temp sensor

There used to be a website I used for wiring diagrams but they've since blocked that feature. Any ideas of free sources for now?

 

[richfinn]

There used to be a website I used for wiring diagrams but they've since blocked that feature. Any ideas of free sources for now?

Public library might have Haynes or Chiltons manual

Try these generic guided tests from PICO, they will work with any scope BTW

https://www.picoauto.com/library/automotive-guided-tests

 

[texasprd]

It won't be free, but you could buy a 1-vehicle subscription to AllDataDIY.com - wiring diagrams will be included, probably sensor-connector pinouts as well. Check and see if there is a free-trial offer on the AllDataDIY sight.

here used to be somewhere (maybe through NAPA's website) that you could get a free trial period for one vehicle for Mitchell, which is another vehicle-/repair-info service.

The cheaper option is a Haynes/Chiltons manual, but the wiring diagrams are (as I remember) difficult to read. I don't know if there are connector pinouts in either of those manuals.

 

[SuzukiGS750EZ]

It won't be free, but you could buy a 1-vehicle subscription to AllDataDIY.com - wiring diagrams will be included, probably sensor-connector pinouts as well. Check and see if there is a free-trial offer on the AllDataDIY sight.

here used to be somewhere (maybe through NAPA's website) that you could get a free trial period for one vehicle for Mitchell, which is another vehicle-/repair-info service.

The cheaper option is a Haynes/Chiltons manual, but the wiring diagrams are (as I remember) difficult to read. I don't know if there are connector pinouts in either of those manuals.

I've used all data and Mitchell in a shop setting, funny you mention them. I can't with on vehicles anymore all day due to an injury but the urge to solve issues others can't is still there!

I'll see how the DIY does

 

[mbazinet]

Ihave an old school Sun Automotive Oscilloscope fully functional if anyone is interested

 

[Ramblin Man]

This may be an odd question, but what can I do at home to get comfortable with using the scope? I kinda poked this with my meter when I first started learning how to use it, checking voltages, finding grounds. Or even in the car? How can I purposely set a fault so I can see the before and after?

I have the money for a meter but until I learn more or have a practical reason to apply it or "practice", I'm not going to buy it, as much as I want to!

When I got started with scope usage, in 1990 something, I bought a Fluke 98 that came with one of these. I played with it at home to get used to the scope. It helped me a lot.

https://shop.snapon.com/product/WaveForm-Demonstration-Tool/Generator,-Diagnostic-Waveform/EESX306A

 

[theoldwizard1]

Ihave an old school Sun Automotive Oscilloscope fully functional if anyone is interested

Pretty useless unless you have an engine with a distributor. Cool looking garage art !

 

[theoldwizard1]

Wiring diagram!!!

You really need to know which wire is signal/supply/ground

There is slowly building group of people complaining about this ! It is directly related to the "Right to Repair Electronics" group.

MA seems to be leading the charge, but you can bet automaker are going to fight it all the way !

 

[2ndGearRubber]

This may be an odd question, but what can I do at home to get comfortable with using the scope? I kinda poked this with my meter when I first started learning how to use it, checking voltages, finding grounds. Or even in the car? How can I purposely set a fault so I can see the before and after?

I have the money for a meter but until I learn more or have a practical reason to apply it or "practice", I'm not going to buy it, as much as I want to!

For basic understanding of EFI systems, I like scanner danner. Very concise and to the point, and shows the tricks that allow one to run without wiring diagrams for basic things. His book is a bit dated, but the fundamentals are great in it. It is more so based on scan tool usage and understanding wiring. IMO you gotta know that first and foremost, as well as OldWizard said, the mechanical actions the EFI system is producing.

For instance, all standard port fuel injectors receive fused power, and the ECU pulses the ground to turn on the injectors and spray fuel. The VAST majority of the time, all injectors share a power feed. Even if there are two power circuits, they're split bank to bank, so one side shares a fuse, and the other shares a second fuse.

So, I have 4 injectors, all sharing a power feed, and all needing individual controls. 1 input spliced to 4 injectors within the harness. STOP! that means all the injectors share a common wire for power. Meaning it should be the same color. That means we can look at just two injectors, and note which wire is the power and ground. The shared color is the shared power feed, and the individual colors are the individual grounds. Because current flows through the fuse, then a splice, then to all 4 injectors, we can then surmise that if we wanted to measure current to the 4 injectors, that we could tap in at the fuse box, and see all 4. Conversely, if we only wanted one, we would need to tap in downstream of the splice.


Literally - scope all the things. Wells-tech, now go-tech? has some good videos. Trained by techs also has some great scope info, all on youtube for free.

Pick something, the injectors for instance. Identify the circuit, understand what each wire is, and what you SHOULD see on each one. Then connect the scope.

 

[2ndGearRubber]

Bonus injector quiz:


4 cylinder engine has the following wire colors on the injectors:

1 - Orange/purple
2 - Orange/green
3 - Orange/green
4 - Orange/purple

What can we say about this system, knowing only the wire colors? And how is it different than the example I listed above?

Which are the control (ground) wires, and which is the power supply?

And why would it be wired in such a way? What decade range/era do you think this vehicle is from?

 

[2ndGearRubber]

Just go back probing wires? Lol

Put on a 10/1 attenuator first, in case you grab ignition primary or injector voltage.

Although any scope with 200v inputs should be 100% fine.


Relative compression
Current ramps
Injector current/voltage
Ignition coil patterns
Cam/crank sensors
ABS sensors
Electronic throttle bodies

Anything you can hook into and see what the signal are, and then try to manipulate to see what happens. Look for youtube videos on all of those topics, and go test for yourself. Current ramps will require either fuse-loops (bought or DIY) or opening up the wiring loom a bit.

Kinda like learning fuel trims:

Graph 02 voltage and fuel trims. Create vacuum leak, what happens? Introduce propane into intake, what happens?

 

[theoldwizard1]

Just go back probing wires? Lol

Basically, yes ! Use T pins from a stationary store for a back probe. If you get to the point of needing a "wire piercing probe" the best are Pomona 6413. Not cheap, but they work. ALWAYS cover your piercings the liquid electrical tape or you will be hating life in the future.

Ignition coils and fuel injectors are interesting wave forms BUT USE AN ATTENUATOR ! This is a good place for two or more channels !

The best ground is always the negative terminal on the battery.

Buy/make some LONG test leads (10'-15'). Use 18 AWG silicone insulated "limp"/"spaghetti"/high strand count wire. Cheap on eBay (sold for RC hobbiest). Put 4mm banana plugs on both end. They do not have to be "sheathed" but the do need to be "stackable" either vertically or horizontally.

 

[SuzukiGS750EZ]

Bonus injector quiz:


4 cylinder engine has the following wire colors on the injectors:

1 - Orange/purple
2 - Orange/green
3 - Orange/green
4 - Orange/purple

What can we say about this system, knowing only the wire colors? And how is it different than the example I listed above?

Which are the control (ground) wires, and which is the power supply?

And why would it be wired in such a way? What decade range/era do you think this vehicle is from?

Orange is common ground, green is one bank, purple the other?

 

[SuzukiGS750EZ]

Oh man, I just need that "aha" moment. Otherwise, you guys are blowing my mind lol

 

[2ndGearRubber]

Orange is common ground, green is one bank, purple the other?

Close:

Remember 4 cylinder engine, so only 1 bank.

All cylinders share a power feed, Orange. The vast majority of things the engine computer controls are ground side switched. Meaning they always have power, ECU supplies ground to turn things on.

That means the other 2 colors are the controls: But look at the pairing, 1 and 4 share a common control wire, as do 2 and 3. On a standard layout 4cylinder engine, what do 1/4 and 2/3 have in common?


They're companion, or sister, cylinders. Meaning when 1 is at TDC compression, 4 is at TDC exhaust. Same for 2 and 3.

Now, this isn't an uncommon setup for ignition systems, it's called waste spark. 1 and 4 are fired at the same time, regardless of which is at TDC compression and which is at TDC exhaust. This allows for "dumber" computers and lower resolution cam/crank inputs. All the ECU needs to know is when the cylinder is at TDC. If it's TDC compression, great, power stroke is created. If it's TDC exhaust, it's a "waste spark".

Thus 1/4 and 2/3 can share an ignition coil each. Instead of 4 individual coils, we have 2 coils, on for cylinders 1/4, and another for 2/3.

__________________________________________________

So, if Orange is the power input, and Green and Purple are switched grounds to control the injectors - What happens when the green wire is provided a ground path?