Trying to repair my ECU.

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1994redram

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This isn't an A body but it's still mopar.

So last Friday I found (what seemed like) a great deal on one of my dream cars, a Viper GTS! I looked at it and decided to buy it knowing it had a misfire and ran rough. It's pretty clean for its age and only has 34k miles. It had the original plugs, wires, belt, etc. I did a complete tune up on it and it runs MUCH better now. However the misfire is still present. I have a P0201 code which translates to cylinder 1 injector circuit. I tested the injector, checked wiring, etc. It all pinpointed to the ECU. So I called around and a refurbished one is only $1999.00...

I don't really have the spare cash for that at the moment. So I opened up the ECU and traced the circuit and found the transistor (I think) is shorted out. I scraped off the silicon and it's very obvious that its burnt. Its a surface mount and would be pretty simple to replace IF i had a replacement. I scraped the silicon off of a couple other matching transistors to get the numbers. The board is made by motorola and looks like they have the Motorola M and R7N L3055 on them.

Ive done a decent amount of soldering before and feel confident enough to do it. But I'm not sure where to get parts and how to choose the correct ones. I know one of you FABO guys will know where to find a suitable replacement.

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im no help on the components except to check digikey and mouser.

Here's my thoughts: 2001-2003 NGC1 pcm have coil drivers go out all the time. So there's a lot of repair guys that advertise PCM repair service.
Repairing a coil driver is similar to what you need on that JTEC PCM. I'd ask the googles and inquire with one of those shops. Just don't tell them its a VIPER pcm, but just a run of the mill JTEC. So you dont get the Viper up charge
 
Would hot air soldering be enough? Im thinking so. If you googled the number it should come up somewhere. You likely have to buy a box of them, but probably cheap like dirt.
Used to be a place i bought electronicals from, was called electrosonic.
Transistor, need to know polarities and wattage methinks.
 
Those transistors are huge. Get a good soldering iron. Clean off as much of the clear coating as you can before you start in. I disagree on the order of removal. Go for the large end first the small leg end will bend as you heat and lift the big end. If you can get some good solder wick that might work to clean the pads up after it is removed.
 
If you can just clip the leads then heat the solder on each leg one at a time and pull the leg out with s pair of long nosed pliers. You will then have to clean out the circuit board holes with a solder sucker or use solder braid to wick it out. You might want to change the injector that's connected to that transistor as it could be bad and it pulled too much current through it. Good Luck
 
If you can just clip the leads then heat the solder on each leg one at a time and pull the leg out with s pair of long nosed pliers. You will then have to clean out the circuit board holes with a solder sucker or use solder braid to wick it out. You might want to change the injector that's connected to that transistor as it could be bad and it pulled too much current through it. Good Luck

It's a surface mount. Shouldnt need to wick out any holes or anything. Its a flexible printed circuit board. It's glued to the case of the ECU. Pretty weird.

I replaced the injector already. They have a strange looking injector but luckily found one local at AutoZone.
 
It is possible to test the transistor using diode setting on multimeter. There is an intrinsic diode drain to source as shown in data sheet. Check that with diode test. Bad part is most often low Ohms, both polarity. Using Ohm setting, check gate to source, often 10K or greater, in circuit. The 10k or more is a pulldown, to avoid gate float during bootup.
 
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I took apart a "remanufactured" ECM once to see what they did to it. Description says they fully solder everything and perform any known updates. Reality is, they simply cut a tiny portion of the factory rubber coating to expose the one tiny transistor that failed. They replace only that one part, then squirted some RTV silicone into the void. It wasn't even sealed completely any more.
Definitely attempt that repair yourself, since you can see where the damaged part is.
 
As a '97 red GTS owner, I hope you're successful!
Is yours a '97 or '98?
PO added stripes?

It's a '98. The stripes are vinyl. I plan to have them removed sooner than later. Hopefully the paint isn't faded or anything. If it is, I'll have some fresh stripes applied. I don't mind them but I would prefer a solid red car.

How long have you owned yours? How reliable are they? Feel free to PM me.
 
I'm thinkin solder wick. Make sure you use solder designed for electronics and NOT acid core/ plumbing stuff. Mouser does? service small orders unless they changed policy. Consider getting a little extra flux, a "flux pen"
 
The hard part of soldering might be the transistor tab. The flex circut bonded to enclosure heatsink will suck heat. It might take a Metcal iron or something similar to drive the heat up quickly without excess, completing soldering, in the limited temperature/time specification of component.
 
Instead of starting a new thread...Ill thread my question into this one as I think its appropriate and Im repairing my mother boards.

Im a novice solderererer. I like the adjustable heat irons, but do not know what else to look for. I have a couple of those Weller non adjusting irons and Im going to blame the tool for my crappy work. Ha! Any guru info? Someone said to get the soldererer sucker in the kit. They all seem pretty cheap online. Tips? Tricks?

Thanks FABO! Is this a hi-jack if I place this question here?
 
Instead of starting a new thread...Ill thread my question into this one as I think its appropriate and Im repairing my mother boards.

Im a novice solderererer. I like the adjustable heat irons, but do not know what else to look for. I have a couple of those Weller non adjusting irons and Im going to blame the tool for my crappy work. Ha! Any guru info? Someone said to get the soldererer sucker in the kit. They all seem pretty cheap online. Tips? Tricks?

Thanks FABO! Is this a hi-jack if I place this question here?
I am a electronics technician by trade (actually now my official title is Field Service Engineer). There are couple of ways to do this, there is a solder sucker (a iron with a hollow tip on it connected to a squeeze ball) which is what I'd recommend or something called a solderpault (a spring loaded device that after you heat up the solder you just push the button and it will suck the solder out for you. One other method is to use solder braid to wick the solder out. You just sit the braid on the solder joint you want to unsolder and it will wick out all if the solder from the board. Here are some links.

https://www.amazon.com/dp/B074ZDCTLV/?tag=joeychgo-20
https://www.amazon.com/dp/B00068IJSG/?tag=joeychgo-20

https://www.amazon.com/dp/B073TRWY19/?tag=joeychgo-20
 
Get yourself some junk computer mother boards. All kinds of parts to practice with on them. Your local thrift store or computer shop should be a good source. Other junk electronics is good too. Watch some you tube videos & have at it. Take parts off & put em back on. Practice makes perfect.
 
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