Oscilloscope - Useful Tool?

paulo57509

paulo57509

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The resident electronics expert at the Lexus forum I frequent uses an oscilloscope frequently to diagnose sensor (cam, crank, etc.) failures and as a diagnostic tool. Because of the countless ECU's that control these cars I was thinking it might be a good idea to have one.

He posted this link as an example of one that's inexpensive but capable for the DIY:


They're cheap enough (a lab-grade scope really isn't necessary); I'm curious to know if this is something that is commonly and frequently used.
 
paulo57509 said:
The resident electronics expert at the Lexus forum I frequent uses an oscilloscope frequently to diagnose sensor (cam, crank, etc.) failures and as a diagnostic tool. Because of the countless ECU's that control these cars I was thinking it might be a good idea to have one.

He posted this link as an example of one that's inexpensive but capable for the DIY:


They're cheap enough (a lab-grade scope really isn't necessary); I'm curious to know if this is something that is commonly and frequently used.
Click to expand...
Also, did I miss it in the product description: is that a single channel? You really want to be able to compare at least two inputs.
 
Scopes are cool but are virtually useless unless you have a technician that knows the vehicle systems and knows how to use the scope to diagnose said system. Yes they are good for home diy just be patient and be ready to read and learn
 
There is a reason that 30 years ago every shop had a scope, and now they do not - OBD2.

Its certainly possible if you have a intermittent problem, or maybe a mild drivability problem where you can use a scope to compare the outputs of sensors or similar, but that's pretty rare. Vast majority of the time your going to get a code if something is off, and if not you have all the OBD parameters to look at directly - Fuel Trims, timing advance, MAF sensor output, 02 or lamda sensor values. Usually understanding what those mean and just reading them off a cheap realtime or graphing OBD tool is going to be much easier anyway, since you need to figure out how to get the scope connected to the output while operating vs just plugging into the OBD port.

I think Scopes at this point are relegated to board level electronic repair - so if your in to that - for sure, there interesting tools and not very expensive. You can get a pretty awesome scope these days for a couple hundred bucks. You want multi channel - and the screen resolution does matter if your looking for small deviations of a component or something.
 
1) Any useful scope is going to be a couple hundred dollars to over a thousand. Trying to read usable data from a one channel 2 1/2 inch screen is going to be quite frustrating.

2) It takes a good bit of experience and technical skill to interpret scope readings. It's like a cardiologist reading an EKG strip. It's not like looking at live data on a scan tool or reading codes.

Look at some of Pine Hollow's videos before jumping in.

 
O-scopes come in all shapes and sizes. Two types really; automotive and electronics repair. I took O-scope training way back and it was a three week, eight hours every day course. They are much simpler now, but still require training.



Start at 2:00 to hear about marketing hype and how to sort through the noise.

This guy's channel is excellent IMO for those looking for Automotive O-scopes as he explains the differences between true electronics repair requirements versus automotive repair requirements. He also delves into O-scope marketing and what not to get duped into buying.

The comments also provide great info as well. Most everyone comments that two channels are the bare minimum, but most want four channels. In my experience, four channels is the minimum I like to use - especially in trying to find intermittent problems.
 
Last edited:
spackard said:
Also, you need to budget another $300 or so for accessories.
Click to expand...

This is very important to think about too. Most of the training I got involved being able to figure out what I was supposed to see before I put a probe on it.

The voltage, timebase, etc. All super important - otherwise you will likely smoke your O-scope and turn it into trash or get no useful information at all.
 
SC Maintenance said:
There is a reason that 30 years ago every shop had a scope, and now they do not - OBD2.

Its certainly possible if you have a intermittent problem, or maybe a mild drivability problem where you can use a scope to compare the outputs of sensors or similar, but that's pretty rare. Vast majority of the time your going to get a code if something is off, and if not you have all the OBD parameters to look at directly - Fuel Trims, timing advance, MAF sensor output, 02 or lamda sensor values. Usually understanding what those mean and just reading them off a cheap realtime or graphing OBD tool is going to be much easier anyway, since you need to figure out how to get the scope connected to the output while operating vs just plugging into the OBD port.

I think Scopes at this point are relegated to board level electronic repair - so if your in to that - for sure, there interesting tools and not very expensive. You can get a pretty awesome scope these days for a couple hundred bucks. You want multi channel - and the screen resolution does matter if your looking for small deviations of a component or something.
Click to expand...

I want to disagree, But at the same time.....You make some valid points. Me?...Couldn't imagine being a Mechanic without one.

It takes dedication though, I have a TB external hard drive with nothing but known good & known bad waveforms. I use my scope weekly at the very least.

Just the other day I had a 6.2L F250 towed in with a no start compliant, No codes/DTC's, Zero fuel pressure. Customer spent @$1,500 for a shop to change the Fuel Pump & ECM. Turns out the Fuel Pump Control Module was bad, Diagnosed it with my Picoscope & Powerprobe.

False diagnostics on OBD2 guesses have become a common practice at a professional level which is sad.
 
clinebarger said:
I want to disagree, But at the same time.....You make some valid points. Me?...Couldn't imagine being a Mechanic without one.

It takes dedication though, I have a TB external hard drive with nothing but known good & known bad waveforms. I use my scope weekly at the very least.

Just the other day I had a 6.2L F250 towed in with a no start compliant, No codes/DTC's, Zero fuel pressure. Customer spent @$1,500 for a shop to change the Fuel Pump & ECM. Turns out the Fuel Pump Control Module was bad, Diagnosed it with my Picoscope & Powerprobe.

False diagnostics on OBD2 guesses have become a common practice at a professional level which is sad.
Click to expand...
I don't disagree in the right hands an O-Scope can be a powerful tool. However in the case of the fuel pump control module, could you not have determined the same diagnostic with a good multimeter? I assume you found either a voltage drop across the module or no output at all?

Certainly not trying to persuade anyone not to get one. Just not sure how often a shade tree type would use it?
 
SC Maintenance said:
I don't disagree in the right hands an O-Scope can be a powerful tool. However in the case of the fuel pump control module, could you not have determined the same diagnostic with a good multimeter? I assume you found either a voltage drop across the module or no output at all?

Certainly not trying to persuade anyone not to get one. Just not sure how often a shade tree type would use it?
Click to expand...
Fuel pump control module outputs a duty cycled square wave on either the power side of the pump or ground side or both depending on vehicle. Duty cycle increases and decreases to control the speed of the pump. You can approximate what that waveform looks like with a DMM that measures voltage/min and max, frequency and duty cycle, but that is just that, an approximation. A scope allows you to see the full picture.
 
I was able to eliminate the fuel pump driver module as the cause of the 0 PSI fuel pressure on my 2004 Ford Crown Victoria by using a 10 amp, 30 volt variable power supply to power the pump.

When I set the voltage to 13V and the current to 10A (max), the output voltage dropped all the way to 7V with the power supply maxing out at 10 amps.

I also didn't hear the pump running.

The pump was probably physically locked up and consuming too much current as a result. At 14V that pump would've been consuming 20 amps. Clearly out of spec.
 
Looking through the Lexus service manual, a lot of the diagnostic procedures use the oscilloscope function of the hand-held tester (scan tool). This is the only vehicle I would ever have the need toI have the Vetronix tool so I should be covered should the need ever arise.

Buried in my memory banks, I vaguely recall playing with one of those small oscilloscopes. I have no recollection of why I would have ever purchased one.

Anyway, thanks for all the comments/insights.
 
I do not feel it is very necessary for home use or as a need tool. If you are interested and want one especially to attempt to learn more about how things work and the price is reasonable, why not get one to grow your mind some.
 
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This is arguably slightly more advanced use of a scope but I enjoyed this from scannerdanner. Looking for jumped time by graphing starter amp draw against when cylinders are firing.
 
We own a 87 VW Cabriolet with the 1.8L JH motor with CIS fuel system. The fuel system adjustment with a O'scope makes it run very smooth and economical. Duty cycle adjustment of the frequency valve rewards us with 32 MPG at 70mph. Its our most economical car.
 
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