Mr. Thompson, could i move to Albuquerque and become your apprentice? Thank you for the videos you always post. Every time you post one it feels like i was waiting for another episode of my favorite series. You are in a league of your own. 😄

"I don't have enough leads." --Legend

You are a next level technician. You're an engineer capable of attacking any problem situation. I hope that you can keep teaching us the possibilities in diagnostics.

Berny love it when you said, “…keep your eye on the ball!” Sounded like a real teacher who’s passionate about making sure your students staying focus. I’ve been watching your videos since last year and honestly you are the best (the goat) when it comes to the oscilloscope and everyone else is in a far distance second place.

Bernie you're a legend! Incredible documentaries of your findings.

Great video that goes well beyond this specific issue. My T-bird had the same symptoms. It turned two coil packs were producing voltage spikes (as seen on a O-Scope). I replaced all of the coil packs and spark plugs parts as parts cost was quite low. I am an electrical engineer that just retired from repairing semiconductor manufacturing equipment for 40 years. This reminds me of the most difficult problem in my career We had a semiconductor manufacturing tool that had an intermittent fly back diode. It would fail once every 2 weeks. We used multiple O-scope to track down the voltage spike. A one dollar part kept a million dollar tool down for 2 months.

Professor Thompson your diagnosis is second to none.

A great lesson in every one of your case studies. Thank you Bernie!!

Hour well spent with mr Bernie. Thanks a lot.

Thanks for the great video Bernie! I had one in a semi one time that the VECU locked up and I just installed a relay with a diode in it for the fix!

Awesome case study, thank-you Mr. Thompson!

Amazing diag , you're on top of your game as always 💪

What a great lesson Bernie.Brilliant

Crazy diagnoses this was an excellent video to get him flying again.

Never would of thought of that. Hats off good thinking.

Excellent sir , never disappointed , thanks for sharing .

Electronic Throttle Control (ETC) is essentially a closed loop servo positional system, which will have a closed loop positional (and perhaps velocity) control algorithm (most likely PI). The H-Bridge current control (PWM voltage modulation) is most likely four quadrant control, especially if the ETC motor has a default return spring. The positional information, throttle position and pedal position, is redundant in order to meet a specified safety level of operation. This safety requirement can also influence the processor selection with redundant computational units running in parallel. The most important aspect of the throttle positional information is that it indicates the true position of the throttle plate (at the needed resolution), secondary is in indicating a fault condition.

Great video again Bernie!

Tuning into the ac clutch turning on and off triggering the fault was the instinct that lead to the final test and ultimately the fix. Love not only the scope analysis, but the combination of skill sets that solved the problem. Ps I prefer breakout relays for any relay testing, but it was cool to know of a wire so fine that you can slip it into the terminals without opening them up when the relays inserted. I think that’s also a little bit of old school in there from Bernie! Lol! Nice!

Amazing work. Experience matters.. thanks for the videos

Wow Just Wow Amazing Find and Video as Always

On Nissan relays the fly back voltage is controlled by the relay itself, and unfortunately the suppression feature is not shown in OE diagrams?The diode or resistor is built in. I'm wondering if simply replacing the relay may have repaired it?

Being that the battery is in the trunk, it may be more helpful to look at signals at the under hood main ground to understand what the module voltages are when the engine is running (powered by the alternator). Mainly for two reasons, the first is the long ground reference lead will pick up a considerable amount of noise, the second is we want to understand the I/O signals as close to the module connector as possible, which is under hood or near the firewall. Ideally, ground for troubleshooting a module would be directly at the module ground as a reference. This is important because what you can see is how the power and ground impedance relative to the battery in the trunk can be modulated by electrical overstress.

Back e.m.f. On any relay in all electronics is always needed You obviously no electronics which is needed to repair modern cars. I have put 4001 diodes on relays on old cars because customers said when going from hi beam to low a ticking sound came across on the radio. I love your vids great diagnostics.

Hey! Burnet grate video! Thanks Teddy Moore! 👍👍👍👏👏👏👏

I learned that protection was in every car Ford made with a cycling A/C clutch back in the 1980's. It's in a plastic enclosure about 2 inches long, and taped to the harness by the a/c clutch connector. If it gets damaged or removed by someone, it's going to allow those voltage spikes. I learned it in school and overheard our lead tech and parts manager trying to figure one out one day back in 1987. They called Mercedes to find out about it. I happened to overhear, so I pointed it out to them in the harness. Theirs had an open that was causing a driveability issue then, in 87. So Ford definitely knows and built them that way ages ago. It would be interesting to see if the T-bird doesn't have one? Or whether it's open? Or is the harness damaged? You need an EVTM to see if it's in their diagram. That's the troubleshooter manual. It's not known for having misprints, omissions, or wrong diagrams. It's what ford techs used before computer displays and live data streams just handed us answers like we have available to us now. It sure was good deduction to ask the customer about how you make it act up and when, then think about what systems are in use, and what circumstances the car goes through at the event. The clutch powers off, releases, and the left over energy has to dissipate. It can, so it does, (without a diode across it) go back and kick the processor. That would be bad. If you're at a wrecking yard, you can grab a spare one to use and put in for the test. They're often black or yellow plastic and wrapped with tape on the A/C harness

True Technical Professional

Thanks Bernie!

real good info !

GREAT CONTENT!!!!

great video

Ford normally puts their diodes in the fuse fox with the fuses I've replaced afew when people jumpstart the car backwards.. I see one for the PCM power but not the A/C clutch..

Great case study! Isn't there a diode in the fuse box like most fords? Thanks for sharing.

Been nice to find the diode. I have access to Ford Service Info and it too doesn't show the diode. Bet the coil has it right at the connector, or very close by. Be neat to follow up on this car. Bet the coil is bad too. Thanks Bernie.

Great job BERNIE THANK YOU

Great video as usual, so you set the diode up in reverse bias to absorb flyback because the grd potential would be higher + than the kickback? Is the kickback always negative value? Like the antenna instead of using multiple channels and multiple e-cops. Do you sell those? I had a Pico but now I'm spoiled rotten with the E-Scope and E-Scan. Thanks

To be effective at clamping the inductive electric clutch voltage spike, the coil clamping diode should be at or near the coil itself. On this year T-Bird the diode is on the compressor housing which is only about 8 inches from the clutch coil. The problem with the negative unclamped coil voltage spike is that, because the battery is in the trunk, there is considerable common ground impedance, across which the voltage spike can influence control module ground enough to cause a processor reset. The question is why is the electronic control module resetting? Is it due to loss of power supply causing a reset, or is the modulating ground triggering a reset circuit, either internal to the microcontroller or external at the power supply. The main vehicle grounds should be checked to see if any common splice or connection point is loose or corroded. The goal would be to minimize the return current common ground impedance. If the battery return is through the chassis then the chassis ground connection points should be checked for corrosion. The AC compressor coil diode on the compressor housing is large, perhaps having a power rating like an alternator diode (75 to 100 Watts). The diode is held by a bracket so it looks like you could replace it without replacing the compressor. The ECM Ignition IGBTs (low side drive, pulling the ignition coil to ground) have an on-board active clamp starting at around 420 Volts to protect the IGBT. It is important to get a high flyback voltage to have a high energy spark (transformer action giving a high ignition voltage at the plug), but not too high to damage the IGBT or force it to clamp excessive energy, which will lead to the IGBT failing due to exceeding its safe operating region usually due to excessive power dissipation (component getting hot). If ECM is designed correctly and the vehicle power supply (battery and alternator) have low source and ground impedance (imagine the ECM placed directly across the battery which is next to the alternator as an ideal case), then the high ignition flyback voltage will not effect the power supply or the microcontroller. The term "set gates out" is a reference to randomly and catastrophically changing microcontroller logic gate states which change the normal program flow (e.g. program execution counter in error) and thus will eventually cause a module reset. The ECM I/O, which includes all the circuits on the module connector, are very robust in terms of electrical disturbances including ESD. So, a voltage overstress which results in a microcontroller reset is most likely apart of the module power supply. The ECM can manage high voltages and currents, if the loads do not excessively modulate the power or ground common impedance. The Microcontroller in the ECM never drives coil-on-plug coils directly, they use a smart pre-driver (for diagnostics (OBD-II), usually through a SPI channel) and then the pre-driver powers the ignition IGBT. The injectors are done in a similar manner, the pre-driver powers the injection N-Channel Smart MOSFET (low side drive), in some cases the pre-driver and MOSFETs are on one special power driver IC. Here again the Microcontroller monitors injection power device operation through the use of a SPI channel serial link. The main reason to put the IGBTs at the coil-on-plug coils (known as a smart coil) is not that the flyback voltage will cause a module reset, it is due to power dissipation. The ignition IGBTs on-board the ECM produce a great deal of heat (actually the largest heat producer at modest engine RPMs), which has to be managed (dissipated) in some fashion. This is why when a Ford EEC with IGBTs on-board fail (misfire, ignition out on one cylinder), the culprit is usually the IGBT that runs the hottest in the module.

Master fix... Sometimes power train Network lines to for example 2kw + audio amplifier in boot feed line not properly fitted in engine bay harness making noise and limp mode.for sure

Amazing 👍👍👍👍👍👍

Cool case study Bernie! How exactly did the voltage spike on the load side of the AC clutch relay make it back to the PCM? We didn't see any evidence on the other channels of the scope 🤔

Bernie is the goat

Are you sure that someone didn't change the relay for one that didn't have a diode? Great video

Mr Bernie I have bought the your scan tool about 8 to 9 months now and without luck it just not plotting the fuel trim on the graph when you do that drive

was that a 4pin or 5 pin relay? and was there 4 or 5 terminals in the fuse block? was that the correct relay? wiring diagrams accuracy is more and more becoming a crapshoot.

I defy you to go to any local dealer and find a tech that knows more about how a fuel injection system works. Dude dreams in injection algorithms.

So it can't be built this way or right off the bat this seems like to me it would be present off the showroom floor, but I thin, you are saying either the diode ground is lost or spikes over time make the ic sick enough to malfunction. That would necessarily necessitate a new computer which is only a partial solution for this Tbird. Have to be a big diode with high voltage and current capability.

I would have put a relay with diode suppression. But great video.

Fantastic video. Do you watch scannerdanner? I’ve learned so much from both of you.

Where do you get that information about how the tps code set and micro processor operates I would love to read that information so I can learn more

Is the diode in the fuse box?

Lisle makes a relay tester.

Which type of diode was used? Means parameter…

Question. When the Clutch Relay Contacts "Open" causing the Magnetic Field to collapse, how does the "Spike" get across the "Open" Relay Contacts onto the DC Supply ??

So how does the suppression diode only suprress the inductive spike but not lead the clutch supply voltage to earth?

Can u tell me a way so i can be perfect in this language or book

How does this spike get its way to pcm ?

"I dont have enough leads" - Bernie Thompson, with 8 leads in use.---The Michael Jordan of automotive diagnostics. Pay attention ppl.

I wish I had his skill with a scan tool.

Why didn't the AC compressor have a diode installed in the circuit to begin with. Normally these circuits do

Wish he was my teacher

People complained about electric throttle body whine? LOL

The original relay had a built-in diode and the replacement does not.

I will truly appreciate if you look in the matter for me

MY QUESTION IS, WHY IT MAKES THE PROBLEM NOW. THE COMPRESSOR CLUTCH HAD NOT NOTHING FOR THE SUPRESSION OF THIS SPIKE WHEN THE CAR WAS NEW THAT S THE SAME CLUTCH, WHY IT DOES THE PROBLEM NOW, WHAT IS CHANGED IN THE COIL OF COMPRESSOR CLUTCH.

Hey Bernie, what is the computer "gate" you are referring to in this video?

I guess this one is not a real diagram

The bird won't fly Ha ha ha !!!!!!!!!!!!!!!!!!!!!!!!!!!

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