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-Brad-, Dodge Dealership Tech
Category: Dodge
Satisfied Customers: 8058
Experience:  16 Yrs Chrysler/Dodge Technician. ASE Master Certified(L-1)
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Replaced pcm and alternator, batteries and cables but truck

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replaced pcm and alternator, batteries and cables but truck stiil wont charge. checked by using external voltage regulator and works fine with it. just wondering if there is a fuseable link on the brown and grey wire between alternator and pcm that could have failed.
JA: Have you tested the battery with a voltmeter? And can you see if it's leaking or not?
Customer: new batteries and with external voltage regulator hooked up entire system works right
JA: What is the model/year of your Dodge?
Customer: ]2008 ram 2500 with 6.7 cummins
JA: Are you fixing your Ram yourself? What have you tried so far?
Customer: yes and already stated what was replaced and done. look back at my previous comments
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Customer: replied 7 months ago.
tested new alternator works fine, had my original pcm tested and all systems were working fine on it as well.

Good evening and welcome to JustAnswer!!

My name is ***** ***** I have worked for a Chrysler-Dodge-Jeep dealership for 19 years and I will do my best to help.

What is the voltage at the B+ at the back of the alternator? If 14v then you have a problem from the B+ to the batteries.. If it's not 14v then the alternator is not charging, you need to check the black for a ground and if good ohm the other wire to the ECM. If the wire is good the ECM on the side of the engine is bad, the PCM doesn't control the charging on a Cummins..

If you need anymore assistance feel free to shoot me a reply and don't forget to RATE 5 Stars before leaving the site so I get credit for helping you today..

Have a great day,


-Brad- and 5 other Dodge Specialists are ready to help you
Customer: replied 7 months ago.
the ecm on side of engine was replaced last night. had original tested and tests fine. no voltage when running. when I hook up external voltage regulator everything works fine. again is there a fuseable link on the 2 wires from alternator to pcm or ecm on side of engine?
Customer: replied 7 months ago.
I drove the truck with the external voltage regulator system for 2 months while waiting on the new pcm/ecm/ecu that was flashed for the vin and installed last night with same issue using the new pcm/ecm/ecu installed on drivers side of engine.

I closed your duplicate question..

There is no fuseable links on the two connector wires to the ECM. Have you ohmed the wires to verify they are not OL?

On gasoline powered engines, the charging system is turned on and off with the PCM (Powertrain Control Module) and ignition switch with engine running. On diesel powered engines, the charging system is turned on and off with the ECM (Engine Control Module) and ignition switch with engine running. The field circuit will not be energized until engine is running and ignition switch on. This voltage is connected through the PCM and supplied to one of the generator field terminals (Gen. Source B+) at the back of the generator. The generator is internally grounded. The generator regulates the field using pin-1 of the field connector (high side driver).

The generator used with diesel engines is internally regulated. The generator and ECM communicate for diagnostics, etc. If the generator regulator becomes disconnected from the ECM, it will still operate, but in a default mode.

Customer: replied 7 months ago.
way over my head. the ecm was replaced because dodge dealer said the voltage regulator is built into it. so I got a new one. when installed though same symptoms. no charging. when I hook up my external voltage regulator everything works fine. drove around for 2 month with external voltage regulator and ran fine. when new ecm on side of engine replaced no charging again. I hooked my external back up and truck runs and charges fine again. 14.68 volts. I am figuring that one or both of the wire from the plug on the alternator to ecm have a break in them. I heard there was a fuseable link on the brown grey wire for the 2 wire plug between them so just trying to make sure before I open the wire loom and chase the 2 wires down from the alternator to the ecm on the side of the engine and then testing them out to make sure they are okay. I seem to understand what needs to be done better when answer is dummied down for me. I have done mechanics on diesels and gas engines since 1985 but sometimes need answers dummied down.
What is your VIN number so I can grab a wiring diagram?

I attached the wiring diagram.. You will need to ohm the Brown/Gray to pin 7 at the ECM..

Customer: replied 7 months ago.
That's what I figured. I figured that one or the other once or both need repaired from the plug to the ecm. Ill let ya know what I find. thanks for the help.

I hope this helps you and in the future feel free to request me for all your Chrysler-Dodge-Jeep needs..

Have a great day,


Customer: replied 7 months ago.
Couldn't get a wire diagram thanks for that. I know its only about 3 ft of wire to chase out, but needs to be done. I have new wire loom to replace the old when I take it off. have had to do this in the past. will test wires first though. I would rather troubleshoot and find the problem rather than be parts changing until I find the problem. dodge dealer hear already cost me $820 by doing that and then I had my original ecm tested and it was fine. pulled the new one and it tested fine as well. figured I'd give this a chance. again let ya know what I find. get back with ya in about an hour and let ya know what I find.
Customer: replied 7 months ago.
dude you are awesome. will let ya know what I find. I'll get back with ya in about an hour with the results. thanks for the diagrams. big help.

You are very welcome...

Customer: replied 7 months ago.
from the 50 pin schematic you sent me and the wire diagram I need to test wire for field gen. at pin 40 and gen. sensor wire at pin 28 to plug on alternator. looks pretty easy pin 7 is for fan clutch on my truck. went under truck already and seen the brown grey wire at pin 40. not pin 7. I really appreciate all the help let ya know what I find.
Customer: replied 7 months ago.
have continuity on both the re and the brown grey wires for pins 28 and 40 to alternator/generator. wires are good. ecm is new and doing the same as the original. hooked back up my external voltage regulator and charging just fine that way.

Add anther ground on the black lead to the frame or ground and tell me if the alternator starts charging..