The No-Throttle Lexus (99 GS400 - P1125)
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- Опубликовано: 12 ноя 2024
- Owner of this clean 1999 Lexus GS400 bought it an an auction with throttle problems.
It's setting a persistent P1125-Throttle Motor Control Circuit.
He limped it from 3 hours away to my shop for a diagnosis.
Parts cannon has been fired: used throttle body, motor, and reman ECM.
Place your bets now!
IVAN'S PICOSCOPE WAVEFORMS:
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THINKTOOL PROS:
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Enjoy!
Ivan
What you're doing is extremely Technical and not many shops that I know of even go into that kind of detail. So great kudos to you and keep on being as diligent As You Are. All the best from Canada
Great way to start my day is a Pine Hollow video with my morning coffee 🫡
It's not shorted, it is open. The ECM has an H-bridge (4 mosfets, one that drives to ground and one that drives to power for each wire) to drive each side up or down. In the fail waveform it is able to drive the PWM side down but the other side which is supposed to be connected fully to power goes down with it because the high side mosfet is open. Without any connection, the voltage is just coming from the other side through the motor coil, and of course current is zero. I wonder if you could trick it with a test light to power...
Precisely correct! I wonder if there's one chip controller or separate transistors that can be replaced?
@@PineHollowAutoDiagnostics It is pretty typical for H-bridges to be a single IC with all four mosfets in it (though discrete fets is possible too of course). The IC is a lot simpler because otherwise you need gate driver circuits and you also need to carefully design your system to prevent "shoot through", where the switching speed of the mosfets is not the same and as a result there is a segment of time where both the high and low driver on the same line are on....blowing up the circuit. Premade ICs handle all that in a reliable way.
Jessica, you are a genius. Impressive take.
@@Zeus-wl2pl I just have an EE background. But, I really have trouble with strange driveability stuff. That is the witchcraft! :)
@@jessicav2031 awesome stuff, Jessica. Now I feel stupid. 😂
The fact that the two PCM's had faults in the same area, just different faults is weird! It is unfortunate your customer bought a PCM that was faulty, but to have the manufacturer of the remanufactured PCM initially seeming not want to know about it is very disappointing. I am glad your customer did not tolerate the BS. Warranty is warranty, to not honour it, or even not want to honour it is disgraceful and shows the true colours of the business.
Fly by night
This issue is probably something the reman supplier either doesn't test or can't test.
Pirates...that's what they are...@##%^
@@sewing1243 That is my opinion also. They may have tested the rest of the ECM engine functions and skipped the one Ivan dug into. I think Ivan is thinking on a much higher level than a lot of other techs. I'm still not certain about his explanation.... but then, I don't mess with Lexus autos either. Thanks again, Ivan, for an interesting video!
The PCM could have a couple different revisions. (speculation). Think about how many engines the PCM must fit into. Mess up the coding for which model and not working. Plus the failure could be the PCM resetting itself into failure mode and never getting out on both.
This is funny because I also ordered a PCM from FS1 and it arrived with the EXACT same problem. That really made me question my diagnosis. They were happy to warranty it, though.
We haven't seen Mrs. Pine Hollow in a while. I always liked seeing her in videos. Even if it was just a quick smile for the camera.
And your pup too. Hope all is well.
As a junior engineer I was assigned to solve a safety mitigating issue. In retrospect, I may have been set up to fail. I studied the electronics, mechanics, and software for several months. Conducted many experiments. Back in the day I had a Fluke, a logic probe, a TI calculator, and my engineering notebook (we didn't have laptops, etc. back then). Read and wrote code in hex. Struggled with months of failure until the "eureka" moment. I immediately documented everything. Hours after submitting my report I was ushered into an executive office. My engineering notebook was confiscated. I was terminated on the spot. I failed. I was ashamed telling my family of my failure. A day or so later I was rehired by the research branch of the operation. worked for over 30 years mentoring and solving difficult problems. Wish I had Ivan on my team...
Great story! 😃
@@PineHollowAutoDiagnostics It was difficult. Am Asperger's. Don't know how to give up on fact. Ultimately battled falsehood to demise. Oh Well (Peter Green era Fleetwood Mac)...
Sounds like flagshit 1 have a halfbaked testing system.
They need to sharpen up on there diags.
I'm happy for the owner of the car, at last it works 😀
That is absolutely wild that the new PCM has virtually the same failure, without someone like yourself with some serious scope abilities, this would have sent any normal technician, myself included, for a serious headache. Nice job
Always great videos Ivan. I do find it sad that automakers removed the simple $50.00 throttle cable and easy throttle body we have all been used to.
You found the problem with the two pcm's. That's what counts. The owner finally got a good one, hopefully a reliable one.
This was a great video. I struggled for a while following the scope and what you were saying but the bonus footage really made things clearer. Pretty cool diag on this one.
The whole time I’m looking at the time left in the video thinking oh we’re definitely getting closure on your diagnosis. Very cool and precise method of making that call!
Not only are you thorough on the diagnostics but the video with bonus and followup tells the "total" story. Your videos are as good as the diagnostics. We learn from you how to rationalize unexplainable anomalies to solve problems and get results. Thanks for sharing.
WOW Ivan very nice diagnosis! You did not get side tracked by a "reman" control unit. Good for you to stay on track and get to the real problem!
It would drive me nuts to have the owner pacing behind me like this guy was.
He's a mechanic so it's not like having a someone asking dumb questions and bothering you . . .
Ivan, I love your channel, watch it all the time, and will continue to do so. But sometimes your so far above me it makes me gasp for breath. Suspect I'll be studying your wave forms a re-watching this one for a while. Just looking at a few of the comments you've certainly peaked the interest in a few other very smart viewers. Whew! Thanks for Sharing!
You Sure Are A Gluten For Punishment Ivan 👏 Bravo On The Diagnosis
Ivan. Great job as usual. I love the fact that you never give up!
Wow blown away by this one! Really tough diag. IMO. Great job.
Ivan, i tried to follow everything in the video, but it blew my mind trying to understand it all. My brain hurt lol. It was difficult to understand the top direction or down direction. I kind of understood that after watching 3 times. I get it, the driver is bad in the ecm trying to control when it can't!
Great video!!! Good job figuring out the problem!!
Ha it took me a bit of thinking to see the pull up or pull down strategy of the drivers 😉
Now that is proof. It's not easy to interpret raw data and you are very good at it. Just had to get your head in the right place first. Very satisfying bonus footage. 👍
Wow.
I’ve never attended one, but what you’ve just presented has gotta be what an Ivy League Electrical Engineering class must be like... wow...
"Wait a minute! This diagram is not for that, it is for the clutch! never mind dudes...." What a Great Mechanic!!!!!
Ivan you are a master mechanic bro!!! I watch your videos all the time. I have learned alot!!!!
Wow what a challenge, great detective work Ivan, what's the odd's to have two bad ECM's. Hair puller.
It was informative to try out the replacement ECM and compare waveforms 🙂
Imagine how simple the life of the car owner would be if he had a car with a good old fashioned throttle cable. I've never been a fan of electronic throttles on vehicles. They are just overkill for what is needed. Nothing like overcomplicating something. I get it that it does away with a cruise module to run cruise control and the ECM now does it but is it necessary. Go back to a separate module for cruise and give me my old style throttle cable back. That's why cars/light trucks have had throttle position sensors for years now.
It wasn't just for cruise control purposes. There are other reasons for allowing the ECM to control the throttle mapping, like changing the throttle feel or masking the drivability impact of emissions strategies. In some cases like with the BMW VANOS system, much of the throttle control isn't even done with the throttle plate at all.
@@RobertHancock1 It's a dumbass setup, doesn't matter to me what it's used for.
nice going ivan you got it in the end good call
Hi Ivan ,when you said the owner had another ecm i thought what if it's from the wrecker and has the same issue? Then you said it was reman. i thought OK,maybe it will work,then i saw the little dents on the lid and thought it's used ,OK. BUT WHEN it failed and you smartly compared the readings ,i immediately thought {ALL THEY DID WAS RE-BADGE A WRECKER ONE AND SHIPPED IT.} now I'm not saying that's what they DID, BUT,hahahahah thanks Ivan
I once faught with fs1 for weeks on getting credit for 3 dodge computers. ALL three were supposed to be tested and repaired by them. Each had a different problem then the others but fixed the original problem..they need a better customer support team and quality control. The first handful of times, I was like hey, I found a decent reman place..only to be let down over and over.
Never deal with flagship 1. Horrible company. I tried them several times, sucks having to ship an ecm back and forth to them half a dozen times before they get it right.
Had the same problem with them
Ivano back to it again nice one really loved it,
If it was your car , I bet you could have fixed the PCM on our kitchen countertop hahah. A single H-bridge driver circuit to fix should be easy for you that's no where near your amazing skills and technique.
kudos from Ethiopia.✌😉
A simple pedal and they put all that crap on it.💩. Thanks Ivan Great video.
I feel like Ivan is being nice when he says, “Flag Ship 1 is hit or miss.” Flag Ship 1 is miss or miss. 😂
Lol they definitely don't have a stellar reputation 😂
About 99,9% of the cars have a fully functional engine computer. So when a car crashes and the parts get sold on eBay, it almost always works.
Exceptions are interior parts like the radio, junction box etc, since they often leave the crashed car that does not have any windows anymore outside for a while and water gets into the car where it is not supposed to go. But for an engine computer that lives under the hood, I would always choose a never opened eBay part over a repaired one.
Noo. This is very hard call to make(ECM) without having a known good waveform for the M+ and M- circuit 😱And this car is 1999.. 😱 PS : Great to mention Maic Salazar. He's really good at repairing modules. I still can't find enough time to watch his module repair lessons for beginners. The whole series is about 7-8 hours long , and i have to watch every single video multiple times. 😫
I saw the 'CL' and thought, "That's it! It's Cyndi Lauper's fault!"
So, you weren't the only one thrown off.
This is exactly why you can't fire the parts cannon at problems. There's always the possibility of a defective new/reman part. You can't assume a part is good just because you already replaced it. If you find the problem by troubleshooting and testing, and you understand how the system works/supposed to work, you can be confident in your diagnosis and you'll know that your new part must be defective. But I'm probably just preaching to the choir here...
Now I'm questioning installing my fs1 ecm for my '95 F250 because this is the second video of yours that I've watched that had failed fs1 ecm's. My bigger problem is I got the ecm late last year and have yet to install it. I primarily got it for emergency just in case.
I like the high tech bonnet stay!
All they had to say was flagship 1…
Had a customer on a nissan use this company… went poorly… a used ecm from junkyard saved the day
I like the anticipation I get till I understand you fault finding fully, but I had a laugh when your missing something, wish I could be your apprentice.
I have a few of the 1uz vvti ecm which have failed, some for this code fault too. I also have a bunch of throttle body to repair as they also suffer issues.
I've seen this throttle body on the 2UZ-FE but never knew it was designed internally this way (with a magnetic clutch), though the arrangement of wires going to it certainly didn't fit the norm. I just assumed the bulging part opposite the TPS was an IACV since there was a mechanical cable on the throttle body.
Must be an "evolutionary missing link" between the old style cable throttle bodies and the current style cableless ones.
Thanks for the exposé (though I'm still trying to wrap my head around its mode of operation).
Here's what FS1 is gonna say: the reason your original ECM failed and also our reman ECM failed is because something is wrong with your throttle body and it damaged both ECMs.
Exactly! But maybe it did? Service data specifically wants you to test both the motor and clutch winding for resistance (and its actually rather high in, Kohms, so low resistance or a short may cause damage). Unfortunately, no resistance checks were done and no comparisons between the replacement TB vs the original TB. hmm...
FS1 may actually determine H-bridge driver damage on both the original ECM and the replacement, concluding that there was in fact a short circuit in the wiring or TB that destroyed both.
@@ecaparts The P1125 clearly has a strategy to disable electronic control during multiple high current scenarios. Not saying it can't still damage the driver but they have done a reasonable job preparing for over current scenarios, from instant transients to more sustained high loads.
@@ecaparts But the new ECM fixed the problem.
@@ecaparts It seems it would have "destroyed" them both the same way. It did not destroy the third one . . .
Good Job!
I had a ls 400 same computer had to replace the capacitors in ecm ran great afterwards
Ivan would you tell us what type of oscilloscope you are using right now along with lap top am very enthusiastic about the work that you do thanks in advance for you replay
Do you think manually working the throttle plate could send a feedback voltage back to the ecu? Frying the driver? That could explain both ecus having the same issues maybe?
Worked developing IC's for automotive/industrial networks back in the 80's and 90's. The vision was to reduce the wiring harness to battery, ground, and network. Every component would be a node on the network. We all know how that worked out in automotive. Worked on automotive EV - get a clue...!
Was an engineering 'jack of all trades'. Wish I had focused on agricultural engineering.
Financial engineering is where to money is. Lol
This was an awesome case study, and the weird part...I followed you Ivan!!!
That's awesome Roxanne!
I love this! Simple yet fascinating diag! Awesome Ivan! 😊👍🏻
I had a similar problem on a 1998 Accord.... you'd have to push really hard when first started to get the throttle to open, and then suddenly it would open making the car lurch forward. I had to completely clean the throttle body, and (I believe) clean the mass air flow sensor and it was back to normal.
Bonus footage and follow-up with a conclusion. My favorite!
excellant video , I wonder with just KOEO not in limp mode u could connect across those two wirers with led logic probe to see polarity change operating pedal as a test to check pcm control
Your a dangerous man, I hope you know that. The more I watch you , the more I "convince " myself I can "logically" follow your example with my scanner. Now, for my piece of mind and I am sure many other DIY'ers how about coming up with a " RETURN TO BEFORE THE IDIOT TRIED TO FIX IT " CODE so we can limp to you and have it fixed properly.
Hi Ivan, just wondering about the "closed" direction for this throttle body. If this is just a small range I am wondering if this is essentially the idle control segment of the engine management. Perhaps this part of the signal comes from the ECU to make the idle work smoothly? I am down here in Australia and owned a LX470 and the ECU's were different from the American models.
A good case for not using abbreviations: clutch vs closed.
Another weird problem 🙂 Although it's a head cracker for you, I really enjoy these cases 🙂 And this acts as a derivative of Murphy's Law - when you're stuck, no matter what you do, you end up with the same problem - what are the odds?
Oh, how I long for the old days with NO ELECTRONICS.
If only they ran as clean . . .
That is some fascinating stuff with the wave forms. But when you don't know what a "good" wave form is supposed to look like, it all gets a bit confusing.
Dam good job ivan that old boy should have gone to the dealer in the frist place and buy one .well done.sam
Last reman pcm I got wouldnt shift my transmission and they wouldn't respond to my calls. Had to do a Visa chargeback
Let just plug it in and see what happens, I like that. Both of the ECM were bad Flash point time for you to step up.
I have a 2000 GS400 and having a low idle problem when it's in gear at a stoplight I have to turn the air on to bring the idle up a little bit. Just curious if you knew anything that would help me fix my problem.
why does the throttle position sensor not go to 0? im thinking if the TPS is not in aggreement with the throttle motor positioning it may go into default/. the throttle position sensor was at around 14 percent in both normal and default.. that doesnt seem right.
I have a 98 audi very similar system the motor is only for idling , the rest is feedback to the ecu to control the engine , you have to adapt the throttle body.
Sweet diag Ivan. Thanks!
Those V8's are a pain in the butt anyhoo.👍😁🇨🇦
What was the point of having a cable to the throttle body and couple it with an electric magnet?
Now, after you have watched this entire video, and contemplated the fact that the throttle plate used to be controlled by a simple mechanical connection directly from the gas peddle, tell me we are not going BACKWARDS! That "fly by wire" throttle assembly must weigh around 30 lbs. What happened to weight reduction to improve mileage? We knew back in the 60's that electrical problems on vehicles were what would leave you walking. So what, in their infinite wisdom have all the manufacturers done in the name of " features?" You guessed it! Just look at the nest of wiring and computer modules under that hood, in a hostile environment where the temperature swings are enormous, where moisture intrusion occurs, and where mice dine on the soy based wire insulation mandated by the EPA. HOLY MOLY!
Bi-directional motor control uses an H-bridge set up. Probably wouldn't be too hard to find on the PCM and test and replace. If one were so inclined to have a good spare PCM. It could be in one package or four separate components.
Those older models have broken solder at tps, seen them on is300 models and many mechanics have nightmares finding problems
Great Job as always.
That clutch circuit is probably a fail-safe. Imagine what would happen if the ECM commanded the throttle yo go wide open. That would be very dangerous. The ECM must monitor the current to the throttle motor and if it gets too high it maybe cuts power to the clutch to mechanically disable the motor control. At that point you're left with a partial mechanical throttle limp mode.
Great job though.
Hey, look at that! THIS time it was the engine computer, Ivan! 😆
awesome job which picoscope are you using
Don’t forget to check the fuse labeled etcs, which reads like etc, but it’s not. Mine blew while changing the battery somehow.
At least we know that the failsafe protocols are trustworthy
I would buy a yard sale pcm before I would buy one from Flag Ship 😳🙄
Ivan, if you had a known good engine module, I think I could prove to you that you could diagnose this problem (PCM drive circuit) using only a current probe on the motor leads (After confirming the clutch is working). In other words, if you could see the motor current waveform of a good PCM in the different directions with your current probe, with perhaps an adjustment to the scope lowpass filter well below the bridge switching speed, you would be able to see a bad driver in the H-Bridge very easily.
What if you DON'T have a known good ECM?🤔
@@PineHollowAutoDiagnostics In general 4-Quadrant (+ regen, sending return spring energy back to the supply) switching (chopper) H-Bridge servo (positional) control for electronic throttle, in satisfying the motor current requirement for torque (and by extension response), is based on a lot of engineering motor and control theory, which is easier to learn (visualize) if you first look at an actual working system and then work your way back to how the drive circuit works and then how the control loop works.
What you will find is by looking at the motor current you can see if the bridge is working properly in each operational quadrant with the added dimension of accounting for regen energy from an energy storage source (like a spring, or for a rotational system, momentum) by looking at H-Bridge drive signals.
Traditionally, if you look at established 4-year EE degree undergrad coursework you will find a course in Electric Machines and one in Basic Control theory. From a practical standpoint in the motor lab you will first study how a DC PM motor is operated to achieve speed control and then positional (servo) control. I think it is easier to first learn speed control and then move to servo control, although the sequence is largely the professors choice. However, if you just take time and study a working actual system you will understand what the theory is trying to describe. And you are very talented at instrumentation, generically called data acquisition systems.
I find a lot of the interaction of electricity and magnetism as a culmination of efforts by Gauss, Faraday, and Ampere as described by Maxwell's Equations, is the long way around when understanding electro-magnetic machines. You don't really have to understand Vector Calculus to understand and correctly apply the theory. If you set up your own experiments you can become very knowledgeable about the practical aspects of motor speed and servo control, and what I think you will find is the primary need to monitor the dynamic aspects of current through the motor windings.
FlagShip One..a division of Klingon Motors.....beware 🤪👍🇨🇦
4:05 ... Pulling up multiple graphs like that is the one thing that the xtool D8 cannot do. It will only graph one thing at a time/ or you can "combine" 5 different pids onto the same full screen graph, (which gets very busy with all the lines overlapping) -- but it doesn't do multiple mini-graphs like this thinktool; and that's a bummer. Otherwise the D8 is actually very good a making keys. I have a 2002 Acura MDX and you can't make a key without pulling codes from the computer-- and the D8 was able to do it. So that's cool... I hope they update the graphing abilities though.
Make a key? Like grind it? 🤔
I'm sure he means programming keys. Lol
@@PineHollowAutoDiagnostics Have you never programmed a key? interesting. You have to go get the physical key copied -- it only costs $1 per key at most hardware stores. But then the key has a built in transponder that needs to be programmed. Some cars like Acura or Nissan require a special code pulled from the computer-- and if the scantool doesn't pull it up, then you can't program the key (which can be really annoying). Newer cars have the keyless system that's more advanced, but I've never programmed one.
Sorry for owner . Bought Toyota supposed reliability fired large caliber parts cannon and had to consult zen master for fix
Ivan do you have any video;s on how to change the a/c clutch magnet ?
Yeah... Look up Nissan Versa
People from all around travel long distances with these very odd problems. If that 2nd computer is anywhere close to being the correct one, it would have to be a common problem to have the exact same analog support circuits fail, you think you could find talk online if that were the case.
That other motor may have shorted turns, which could blow the junction in the H bridge FETs. It could blow any of them depending on the duty cycle and whether opening or closing the throttle at the time that one of the FETs gave in to the heavy current, so a bad motor could have destroyed both computers in the two different ways
Can you make one working computer from both , 1 closed driver from one unit and one good open driver 😁
success
that right there highlights longevity issue and dumpster full of parts required for over complicated system designs .
For sure on paper and theory electronic throttle has some advantages but in real world long term it a ballache, money pit and more component waste in dumpsters/landfill .
driver cycle for throttle control is pretty extreme thus highly prone to failures, good old cable and ICV wins for me, lasts decades and so simple, electric parking brake another great example of removing a cable for unnecessary electrical system control creating more problems and more scrap parts than it truly worth in any form of functional benefit ...
Would this affect the transmission as well? I'm getting this error ans symptoms but also the tyranny is now rough and tiptronic no longer functioning on my 2004 lexus is300
Should note that these symptoms and codes began after replacing catalytic converter
excellent video, thank you
Super interesting! So it appears there are 2 windings in the motor in series. I struggled at fist, thinking it was a stepping motor with 2 separately driven windings and the difference in phasing would determine direction. But since the windings are in series, it's just a PWM-driven DC motor. That being the case, I'd expect that the polarity would reverse to drive closed, with the PWM duty cycle increasing to drive closed with more force. I didn't see a reversed polarity on the scope, but one would probably need the scope across the windings instead of referenced to ground. The drawing was technically correct, but it was still drawn in such a way as to cause confusion. I'd never seen or heard of this arrangement with a clutch to allow fail-safe operation, so it was a very interesting video. I'm not going to use the slang, but there is a word often used in industry to describe off-the-wall arrangements like this. My father has a 1987 or 88 vehicle with a PWM solenoid controlling fuel bowl level in the carb and having an oxygen sensor for mixture feedback. I consider it to be a similar one-off arrangement that few people will ever diagnose or repair. I'd expect the proper computer to be difficult to get, also.
Yes the service data and description of operation are lacking here. I am more familiar with GM and domestic vehicles which typically need to be driven open and closed (without power they freeze in position). Not exactly the case with this one. This TB has a strong return spring to the close position. So does it NEED a reversed voltage to the TB motor? NO.
Also, there was no reverse voltage indicated on the scope AND the schematic specifically showed the + and - polarity to the TB motor. Does that mean the polarity doesn't change?
Unfortunately, I'm left with more questions than answers:
Is this NOT an H-bridge driver?
What is the clutch circuit for?
Why does scan data show TB close % if there is a spring return??
I wish we had more information with this one...
The polarity change is when each wire is pulled to ground/hot. When the blue is high and the red is low, the polarity is going one way, when the red is high and the blue is low, the polarity is reversed.
Had the same exact problem on a friend's car. Alldata had me test resistance on a circuit and it failed the Ohm test and said the part was bad, replaced the part and same problem.?
Same car? Follow the diagnostic steps in this video.
Watch “the Cartune company” from New Zealand on these Lexus V8s etc as they specialize in these engines with conversions etc
Kelvin is very smart with these (plug for my mate down the road from me)
Similar issue worked out on Lexus GS by OZ Mechanics: ruclips.net/video/zSlHLdLmTF4/видео.html. Was the PCM.
Great video Ivan liked it!!
Question:- Why this throttle body has 2 duty cycle controls!
Very curious to know!
The PCM is controlling four transistors that control the polarity of the throttle motor's power and ground circuits. One set of transistors (high and low) is used to rotate the motor in the open position that is against spring tension. The other set of transistors is used to close the throttle, but the motor's polarity is reversed to do this. Basically, it works the same way as a window motor, but instead of using mechanical switches or relays it is using a H bridge to control the polarity through the motor. The pulsing you see in the waveform is the PCM controlling the throttle blade position against spring tension to keep the throttle blade at a desired position. You see 12 volts on one wire when one high side transistor is on and 0 volts (ground) on the other wire when one low side transistor is on. That means current is flowing through the motor. The PCM is pulsing the low and high because the throttle is always trying to be closed or opened by spring tension. The throttle is also spring loaded to stay slightly open when there is no power to the motor. That way the vehicle will stay running if power to the motor is lost. The PCM can also close the throttle all the way, but it has to reverse the polarity of the circuit using the other set of the H bridge transistors to go against the closed throttle spring. When the PCM commanded the throttle position closed to the the idle position and needed to reverse the polarity of the motor to do this, the PCM saw no current and shut the motor off. If either high or low side transistors for reverse polarity remain open when commanded on, the PCM will see no current and detect a fault. Remember the PCM sets the code P1125 code if it see less than 0.3 amps when duty cycle is commanded to greater than 80% for less than 0.8 secs.
The magnetic clutch when turned on connects the motor to the throttle shaft. The PCM can turn off the magnetic clutch to disconnect the throttle shaft from the motor. That will cause the springs to move the throttle blade to the default position.
They obviously had a different Mosfet fail in each ecu in the h-bridge motor drive cct.
at 20min mark I started thinking of my old college day experiments with 50% duty cycle when there was a +12V and a -12V power supply rail. when the duty cycle is at 50%, it doesn't move. Perhaps, say the -12V power supply is compromised. It almost seems like this could be a configuration consideration? PC power supplies for instance have 12V, 5V 3.3V but it takes the internal +12V and taps into it to make a -12V circuit for stuff like Hard drives to make mechanical arms move back and forth. I'm wondering if this "similar concept" is at play? Lexus does tend to make higher complexity items.
theses use a h bridge configuration.
+12
high FET high FET
|- -------- -load- -----|
Low FET Low FET
0V
The same can also be done using transistors instead of mosfets.
I was taught not to open the throttle plate on a motor driven throttle body without unplugging it.
The reason was that if you drive the motor too hard it becomes a generator and sends a voltage back through to the ECU potentially doing damage to driver circuits. Could this be the cause of this fault?
As these vehicles get older, someone cleaning the throttle body becomes more likely.
That sounds like an old wives tale to me. That would be some very badly designed circuitry to be damaged so easily.
@@RobertHancock1 I will never have to find out, I pull the plug before opening the throttle just as a precaution.
I can fully understand how an issue might potentially occur and I am just not interested in taking the risk.