Duramax LLY - FICM / Injector Trouble / Misfire - Part 2
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Date: 2020-08-05
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Comments and reviews: 10
Daniel
Our 2004 ( lly) gmc 2500hd 4x4 needs an injector module. We're at 300, 000 miles, bought truck used in '08 with 107, 000 miles. Twice before we had trouble with injector wire harness (they said harness for #2 and #7. I think we could drive 35 mph. This time only 15 mph. Not sure if this has anything to do with module problem, but truck seemed to be using fuel really fast. Then two days before( module went out, I fueled up within 20 miles fuel guage read 3/4. When truck started running like crap guage read empty ( only about 50 miles, but after adding some fuel guage still read empty. While waiting 2 hrs for tow truck fuel guage went past full. Mechanic said probably not related. It's been a few days and they can't locate a used part (they said nobody has a junked duramax ) and new GM part is 750. At 293, 000 miles we lost transmission, transfer case was melted (I believe was the term they used. Transmission shop said they usually only last 150 - 200, 000 miles max. 5, 500 for transmission and transfer case (they rebuilt my transmission but had to get rebuilt transfer case. Mine not repairable. We always keep our vehicles forever and use them hard on our little ranch. So, this far in, I think just get new part. But I hope these computer problems aren't going to continue. I HATE COMPUTERS! I don't understand them and I don't have scan tools to check them. I like old school mechanical.
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Our 2004 ( lly) gmc 2500hd 4x4 needs an injector module. We're at 300, 000 miles, bought truck used in '08 with 107, 000 miles. Twice before we had trouble with injector wire harness (they said harness for #2 and #7. I think we could drive 35 mph. This time only 15 mph. Not sure if this has anything to do with module problem, but truck seemed to be using fuel really fast. Then two days before( module went out, I fueled up within 20 miles fuel guage read 3/4. When truck started running like crap guage read empty ( only about 50 miles, but after adding some fuel guage still read empty. While waiting 2 hrs for tow truck fuel guage went past full. Mechanic said probably not related. It's been a few days and they can't locate a used part (they said nobody has a junked duramax ) and new GM part is 750. At 293, 000 miles we lost transmission, transfer case was melted (I believe was the term they used. Transmission shop said they usually only last 150 - 200, 000 miles max. 5, 500 for transmission and transfer case (they rebuilt my transmission but had to get rebuilt transfer case. Mine not repairable. We always keep our vehicles forever and use them hard on our little ranch. So, this far in, I think just get new part. But I hope these computer problems aren't going to continue. I HATE COMPUTERS! I don't understand them and I don't have scan tools to check them. I like old school mechanical.
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Joe
I was suspicious of some sort of driver module 'cause the Amps: Volts ratio wasn't gonna come from a PCM. I was thinking a quad driver or quick-switching MOSFET. I still wonder why the coil collapse is so long before the spike of 50+ VDC.
. and, yeah. 50V will kick a bit. but it's the Amps ya gotta worry about.
You're laid out across s lot of potential grounds and sticking a probe into places where ya shouldn't. zap!
Then ya gotta sharpen a new point on your probe. BT-DT!
I notice that your probe is long enuff for many re-sharpenings. Just sayin'.
If it wasn't for nothing but your Columbus attitude (seek, and ye shall find) I 'd still watch just for entertainment value. Love ya, guy!
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I was suspicious of some sort of driver module 'cause the Amps: Volts ratio wasn't gonna come from a PCM. I was thinking a quad driver or quick-switching MOSFET. I still wonder why the coil collapse is so long before the spike of 50+ VDC.
. and, yeah. 50V will kick a bit. but it's the Amps ya gotta worry about.
You're laid out across s lot of potential grounds and sticking a probe into places where ya shouldn't. zap!
Then ya gotta sharpen a new point on your probe. BT-DT!
I notice that your probe is long enuff for many re-sharpenings. Just sayin'.
If it wasn't for nothing but your Columbus attitude (seek, and ye shall find) I 'd still watch just for entertainment value. Love ya, guy!
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Andy
Well the mechanic that made the wrong call said he switched the injectors 3 to five I wonder if that injector shorted out the driver maybe as it heated up the resistance went down just enough to smoke the driver. If thats the case then that other injector could short the new driver if that is the case hard to say without my hands in the truck but great job. Even though resistance increases with temp sometimes it does the opposite an amp clamp on the wire once it gets hit observing the amps if they climb you know resistance is going down.
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Well the mechanic that made the wrong call said he switched the injectors 3 to five I wonder if that injector shorted out the driver maybe as it heated up the resistance went down just enough to smoke the driver. If thats the case then that other injector could short the new driver if that is the case hard to say without my hands in the truck but great job. Even though resistance increases with temp sometimes it does the opposite an amp clamp on the wire once it gets hit observing the amps if they climb you know resistance is going down.
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Ozzyogo
I have to admire your tenacity to establish the facts and making the right diagnosis instead of joining the ranks of the royal parts canoneers that we hold in such high regard. In 2004 the European Space agency launched a washing machine size probe 4000, 000, 000 miles into deep space and landed the probe on a 3 mile long comet! 15 years later the car makers can't make a computer to tell you exactly which of their crappy parts has failed. And they want me to buy a 50, 000 pig shown by some of your examples, the dealers can't even fix.
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I have to admire your tenacity to establish the facts and making the right diagnosis instead of joining the ranks of the royal parts canoneers that we hold in such high regard. In 2004 the European Space agency launched a washing machine size probe 4000, 000, 000 miles into deep space and landed the probe on a 3 mile long comet! 15 years later the car makers can't make a computer to tell you exactly which of their crappy parts has failed. And they want me to buy a 50, 000 pig shown by some of your examples, the dealers can't even fix.
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autos
Hey Eric. Did the 50v spike move from injector open in the bad wave form recording, to the injector closed in the good wave form recording? Sure looked that way to me, and if you go by, if you raise the voltage- the current drops and vise versa. The bad form was raising voltage and current at the same time, which theoretically isn't possible. Raise voltage- current drops! That's what the good forms did. Take another look at it again. Take care. Jpol.
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Hey Eric. Did the 50v spike move from injector open in the bad wave form recording, to the injector closed in the good wave form recording? Sure looked that way to me, and if you go by, if you raise the voltage- the current drops and vise versa. The bad form was raising voltage and current at the same time, which theoretically isn't possible. Raise voltage- current drops! That's what the good forms did. Take another look at it again. Take care. Jpol.
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Fourty
Eric awesome video and i agree what kind of Weirdo still does hand writing invoices let alone ask for cash hope IRS doesn't pull an Audit. I speak from experience when i tell ya its all bad but you might want to add those receipts up I am sure you will see it was 2, 300. 00 Ouch! A wise man told me that a clear conscience makes a soft pillow but i guess everyone has to pay one way or another for choices we have made. keep up the good work
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Eric awesome video and i agree what kind of Weirdo still does hand writing invoices let alone ask for cash hope IRS doesn't pull an Audit. I speak from experience when i tell ya its all bad but you might want to add those receipts up I am sure you will see it was 2, 300. 00 Ouch! A wise man told me that a clear conscience makes a soft pillow but i guess everyone has to pay one way or another for choices we have made. keep up the good work
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Victor
You explained it so well I could give you what most likely failed inside the FICM, most likely the trace on the circuit board for the number three injector burned up. Traces are like wires, so basically an open circuit internally is what it looks like. Too bad its years later and you probably dont have the old FICM to pry open and take a gander at. Youd probably see a broken trace going to the number 3 injector control pin.
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You explained it so well I could give you what most likely failed inside the FICM, most likely the trace on the circuit board for the number three injector burned up. Traces are like wires, so basically an open circuit internally is what it looks like. Too bad its years later and you probably dont have the old FICM to pry open and take a gander at. Youd probably see a broken trace going to the number 3 injector control pin.
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Garth
The process was fairly good to follow. The PWM circuit to the FI was explained and made sense why the spike in volts was needed for the first fire to the FI. One thing I noticed at first was, what a clean engine compartment! Your owner friend must have cleaned it up just for you knowing you would be getting your hands in their. Nice truck with low miles for someone that can use it.
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The process was fairly good to follow. The PWM circuit to the FI was explained and made sense why the spike in volts was needed for the first fire to the FI. One thing I noticed at first was, what a clean engine compartment! Your owner friend must have cleaned it up just for you knowing you would be getting your hands in their. Nice truck with low miles for someone that can use it.
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mike
Eric, your knowledge of ossiloscopes operation f excellent, many dealer techs wouldn't have a clue, dealers as many other garages don't spend enough time to find out the correct faults on vehicles, it's nowadays, let's fit a new part and if that doesn't work let's fit another one, modern day vehicles are turning into a proper crock of shit for us guys, well done Sir
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Eric, your knowledge of ossiloscopes operation f excellent, many dealer techs wouldn't have a clue, dealers as many other garages don't spend enough time to find out the correct faults on vehicles, it's nowadays, let's fit a new part and if that doesn't work let's fit another one, modern day vehicles are turning into a proper crock of shit for us guys, well done Sir
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John
I had this same problem on my lly. I guess alot of ppl did. there is a gm service bulletin regarding a chaffed wire harness that passes right over the ficm. You may have inadvertently eliminated the short when replacing the ficm. However, i think your troubleshooting technique is solid. I learn all sorts of cool stuff here! Thanks!
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I had this same problem on my lly. I guess alot of ppl did. there is a gm service bulletin regarding a chaffed wire harness that passes right over the ficm. You may have inadvertently eliminated the short when replacing the ficm. However, i think your troubleshooting technique is solid. I learn all sorts of cool stuff here! Thanks!
reply
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