Gen V L83 02 Jeep TJ wth, crazy alternator issue

marty79

marty79

Well-Known Member
Joined
Nov 24, 2013
Location
Newton, NC
alright guys need a little help please. 02 TJ Gen 5 L83 6l80e, standalone harness, everything else is stock.
Alternator will not charge. We bought the relay kit that wires into the OBD plug (or ECU wires like I did), still nothing... doubler/tripple checked wiring and checked it with the LJ swap I did, same on both
Swapped alternators nothing
We have 2 ECUs both tuned by same guy, both work like they should but no charging..
Swapped ECU with the LJ everything worked the same but no charging??wth
Now it gets weird...ONLY using jeep harness for factory gauges (oil, temp, fuel, and battery gauge) to work and they do...but the fuse box behind the glove box had bad/higher amp fuses, so I replaced them with proper amp fuses and WTH, alternator started working. It worked for a month now but just the other day customer called and it's not charging again.
This is my 3rd swap, did a 06 LJ SAME EXACT platform to the tee and his works perfect..nothing different other than factory harness reworked but we've checked and double/tripple checked harness from PSI and all checks out.
ANY help much appreciated, thank you

(what really confuses me is why the jeep side of this Jeep affected the alternator in the beginning?? I didn't care then, neither did customer, cause it got it working lol, but now that it's quit, I feel like we need to solve the issue of why it won't charge on it's own "chevy" side of the swap...like the other 2 swaps I've done.)
 
marty79 said:
Now it gets weird...ONLY using jeep harness for factory gauges (oil, temp, fuel, and battery gauge) to work and they do...but the fuse box behind the glove box had bad/higher amp fuses, so I replaced them with proper amp fuses and WTH, alternator started working. It worked for a month now but just the other day customer called and it's not charging again.
Click to expand...

Check if the high amp fuses are blow again.
If yes, swap them and see if it charges again.
If yes, figure out why they blew in the first place.
 

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I had a similar issue in my stock YJ (factory ECU could no longer regulate the alternator). I tossed one of these kits on and it worked great. Most of it is OEM old skool stuff, but in the event of a failure, you have nothing exotic to replace.

I would bypass the ECU regulation completely, but you do you.
 
Bebop said:
Check if the high amp fuses are blow again.
If yes, swap them and see if it charges again.
If yes, figure out why they blew in the first place.
Click to expand...
Customer says all jeep and chevy fuses are good..
 
braxton357 said:
Why can you not use an internally regulated alternator on a gen 5?
Click to expand...
I guess you could but shouldn't have to. Its pointless and going backwards. I'm trying to figure out why stock system isn't working as it should
 
I'm not really familiar with the gen v stuff but I'm assuming that's a pwm driven alternator. If so I'd bet the ecu is looking for some info on current draw and battery voltage. Not sure exactly what the sensor would be called but if it's not wired in then the ecu doesn't know it needs to charge. Though they should still default to ~13.8v

If it were me I'd swap the voltage regulator out for a non pwm. No reason to have it in a swap since the original intention of the pwm alternators was fuel mileage driven. Nobody cares about that in a swap.

Metric shit ton of LS/LT alternator info here is you get bored and like to read.

Dirty Dingo Motorsports

LS Conversion LS Swap
www.dirtydingo.com
 
Chris_Keziah said:
If so I'd bet the ecu is looking for some info on current draw and battery voltage. Not sure exactly what the sensor would be called but if it's not wired in then the ecu doesn't know it needs to charge. Though they should still default to ~13.8v
Click to expand...
This is the worst part is he bought this:

RpmExtreme GM Alternator Charging Request Module​

and that was supposed to fix all this crap. My other customer with the LJ Gen V swap bought it and it's worked great from day 1 installed (it's super easy to wire in, kinda can't really screw it up lol). And that isn't a cheap part, it's somehow $250 but whatever, it worked on the LJ swap so I told this TJ customer to buy one and we did....

The even more weirder part is the LJ customer can (like you should be able to) unplug the factory Jeep ECU and doesn't affect the charging or anything but factory gauges...that's how it should be but this stinkin TJ is not the case.
I'm at the point of taking it back to the Tuner, I have a really strong feeling there's something in the background that he didn't turn off or programmed to ignore and that's why it's not charging.
 
But for the life of me, just for learning purposes, WHHHYYY (lol) does the jeep side of things affect the chevy side of charging to begin with???? that is the mystery to solve here....and it bugs the crap out of me....even more since I did the 06 LJ the exact same way, same motor/trans/everything
 
"The only known factory LS application where the stock ECU doesn’t connect to the alternator is the ’98-’02 F-body. However, most of the “computer controlled” alternators on these engines can be placed in an automatic mode by wiring their “L” terminal to the dashboard alternator warning light (which would get switched 12 volt power if your car originally did not have one). When the L terminal is connected to a lamp, the alternator will power up and put out charging voltage. This trick works on any alternator with a four terminal connector where the terminals are marked P, L, F (or F and I on the same terminal), and S. The remaining three terminals are left disconnected."

Did you try this?
 
braxton357 said:
Did you try this?
Click to expand...
No I haven't, I've read that but according to RPM extreme $250 product (like on the LJ I did) you don't need to. But I also know what you're talking about can/should be tuned out of the ECU.
I start Tuning school soon and I can't wait to learn everything about engine optimization/ diagnostic/ tuning/management!
 
I guess I'll try the dash light wiring as you said..I'm open to all options on this particular swap since nothing has worked like it should. Thanks
 
braxton357 said:
"The only known factory LS application where the stock ECU doesn’t connect to the alternator is the ’98-’02 F-body. However, most of the “computer controlled” alternators on these engines can be placed in an automatic mode by wiring their “L” terminal to the dashboard alternator warning light (which would get switched 12 volt power if your car originally did not have one). When the L terminal is connected to a lamp, the alternator will power up and put out charging voltage. This trick works on any alternator with a four terminal connector where the terminals are marked P, L, F (or F and I on the same terminal), and S. The remaining three terminals are left disconnected."

Did you try this?
Click to expand...
That's only on the 4 wire alternators, what he has should be a 2 wire which looks for a pwm signal from the ecu. Generally on swaps and what I've done in the past is put a resistor in to simulate the light.
 
marty79 said:
This is the worst part is he bought this:

RpmExtreme GM Alternator Charging Request Module​

and that was supposed to fix all this crap. My other customer with the LJ Gen V swap bought it and it's worked great from day 1 installed (it's super easy to wire in, kinda can't really screw it up lol). And that isn't a cheap part, it's somehow $250 but whatever, it worked on the LJ swap so I told this TJ customer to buy one and we did....

The even more weirder part is the LJ customer can (like you should be able to) unplug the factory Jeep ECU and doesn't affect the charging or anything but factory gauges...that's how it should be but this stinkin TJ is not the case.
I'm at the point of taking it back to the Tuner, I have a really strong feeling there's something in the background that he didn't turn off or programmed to ignore and that's why it's not charging.
Click to expand...
You over looked something I should have highlighted. Granted I'm going off some assumptions here but anything gen IV or V with a pwm alternator has to have something tell the ecu how much load is on the system. If that's not there the ecu will not output the signal to the alternator.

You've got hptuners now, pull the file and look for any charging related parameters. I doubt taking it to the tuner will fix anything unless you pay him to make it his problem.
 
marty79 said:
The even more weirder part is the LJ customer can (like you should be able to) unplug the factory Jeep ECU and doesn't affect the charging or anything but factory gauges...that's how it should be but this stinkin TJ is not the case.
I'm at the point of taking it back to the Tuner, I have a really strong feeling there's something in the background that he didn't turn off or programmed to ignore and that's why it's not charging.
Click to expand...
Computers work out of input / output.
Something has to be different between the 2 cars.
 
Chris_Keziah said:
You've got hptuners now, pull the file and look for any charging related parameters. I doubt taking it to the tuner will fix anything unless you pay him to make it his problem.
Click to expand...
Broooo thank you, I totally didn't think of this. I guess since I'm just starting online tuning school in few weeks, I kinda just stuck the HP Tuner and new laptop off to the side lol.
 
Bebop said:
Computers work out of input / output.
Something has to be different between the 2 cars.
Click to expand...
Yeah obviously but dang i wish I knew lol
 
Chris_Keziah said:
here but anything gen IV or V with a pwm alternator has to have something tell the ecu how much load is on the system. If that's not there the ecu will not output the signal to the alternator.
Click to expand...
Kinda true,.. but that's what tha $250 rpm extreme part supposed to do or if your good with tuning, you can fix it in tune.
 
marty79 said:
Kinda true,.. but that's what tha $250 rpm extreme part supposed to do or if your good with tuning, you can fix it in tune.
Click to expand...
If you have that standalone driver module the only tune things that need to be addressed are turning off the charing related dtc's.

If that's installed then check your ground and verify the 12v input to the controller and go from there. You'd need a scope to verify the pwm output signals.

Also is the charge wire from the alternator running back to the battery or through a fuse box.
 
Chris_Keziah said:
If you have that standalone driver module the only tune things that need to be addressed are turning off the charing related dtc's.

If that's installed then check your ground and verify the 12v input to the controller and go from there. You'd need a scope to verify the pwm output signals.

Also is the charge wire from the alternator running back to the battery or through a fuse box.
Click to expand...
It goes straight back to battery
 
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