2015 ram 3500 6.7L wont charge, goes into batter saver mode

[j toomey]

I've been chasing a intermittent charging issue for a couple weeks now and am now stuck with the truck not charging at all.

Relevant history:
Batteries are only a couple months old. At startup, randomly wouldn't charge. Finally stopped charging all together. Put a new alternator in, still not charging. Put a new battery sensor on the negative drivers side battery and it starts charging again. Fast forward a couple weeks and I'm back to very rare (one a week) intermittent charging again. I checked and cleaned all the battery terminals and all the wires have good connections with no corrosion. Truck has the single 220 amp alternator.

Today it wont charge at all. Batteries read 11.9-12.1v while running. Am I missing something simple here? I'm suspicious of the battery sensor. Anyone know what the sensor is looking for voltage wise, so I can eliminate that from the equation. I've ran out of parts to replace and I'm stumped with a undrivable truck.

 

[Timd32]

Not sure how reable this screenshot will be.

 

[j toomey]

Not sure how reable this screenshot will be.

View attachment 128509

definitely readable, but any idea what those two wires should be reading or sending to the ecm?

 

[Timd32]

No I can't find any values for the actual sensor.

Looks like you would need to read some data to see what it's sending back.

 

[Timd32]

Might be some info here on the operation.

 

[j toomey]

Might be some info here on the operation.

View attachment 128510

Thank you! I am going to trace all these back again in the morning and if I can't find anything obvious I will need to pickup a meter that is capable of measuring pulse width and dig deeper into it. I'm hopeful it isn't a PCM issue.

 

[DavidC]

Thank you! I am going to trace all these back again in the morning and if I can't find anything obvious I will need to pickup a meter that is capable of measuring pulse width and dig deeper into it. I'm hopeful it isn't a PCM issue.

Probably gonna need one of these
Amazon product ASIN B078WRKZG7

 

[j toomey]

Probably gonna need one of these
Amazon product ASIN B078WRKZG7

at that price I might be better off just gambling and buying a new ECM... If the pulse width isnt correct, wouldn't the only fix would be a new ECM anyways?

 

[Tuesdak]

At that price take it to a dealer or auto electric shop that can likely fix this cheaper. One bad connector will have you tossing money down a black hole in parts that are not the problem. Sometimes knowing your limitations and renting experience is cheaper and gets you back on the road quicker with a fix. You are already assuming the replacement alternator is a good part forgetting WE are the quality control on a patched, rebuilt, or new part.

You may have a bad battery and this needs a load test with the batteries disconnected from each other. The voltage you posted is near dead battery low.

 

[j toomey]

At that price take it to a dealer or auto electric shop that can likely fix this cheaper. One bad connector will have you tossing money down a black hole in parts that are not the problem. Sometimes knowing your limitations and renting experience is cheaper and gets you back on the road quicker with a fix. You are already assuming the replacement alternator is a good part forgetting WE are the quality control on a patched, rebuilt, or new part.

You may have a bad battery and this needs a load test with the batteries disconnected from each other. The voltage you posted is near dead battery low.

Good call, I will chase down the obvious and check the batteries then seek a professional. I hit a major pothole and had some things fall off, so the dealer isn't really an option and will have to find a competent electrical specialist.

 

[DavidC]

Yeah, your not going to check a pulse width without a scope and the first thing is to know how to use one.

 

[j toomey]

Yeah, your not going to check a pulse width without a scope and the first thing is to know how to use one.

I work at a place that has extremely talented electronic technicians and an endless supply of testing equipment, I'm confident I could get that end of things figured out if need be, but I would need to have a "correct" sample to compare to what my truck is putting out regardless. My thought is to go through the list and get some of the simpler things out of the way. I was hoping someone had a similar experience that led them to a fix that was something I am missing.

 

[Tuesdak]

Sounds like it's 6 Pack time with co-workers.

 

[monovasia]

Sounds like it's 6 Pack time with co-workers.

I've been chasing a intermittent charging issue for a couple weeks now and am now stuck with the truck not charging at all.

Relevant history:
Batteries are only a couple months old. At startup, randomly wouldn't charge. Finally stopped charging all together. Put a new alternator in, still not charging. Put a new battery sensor on the negative drivers side battery and it starts charging again. Fast forward a couple weeks and I'm back to very rare (one a week) intermittent charging again. I checked and cleaned all the battery terminals and all the wires have good connections with no corrosion. Truck has the single 220 amp alternator.

Today it wont charge at all. Batteries read 11.9-12.1v while running. Am I missing something simple here? I'm suspicious of the battery sensor. Anyone know what the sensor is looking for voltage wise, so I can eliminate that from the equation. I've ran out of parts to replace and I'm stumped with a undrivable truck.

I had a similar problem a couple of years ago... was an intermittent ground wire... right wheel deck by the batteries...took me the better part of a week to find it

 

[Ozymandias]

Do you have AlfaOBD and know how to use it? If not just stop right here.
You can not fix these vehicles without proper diagnostic equipment.

And no you can not drop in an ECM just like that, they also need to be matched to the vehicle.

Diagnostic is the key, should have been done before the first dollar was spent on hardware.

 

[sag2]

The battery sensor is a LIN BUS circuit, so it just has a voltage output. You really need a scan tool capable of looking at all the data and diagnose from there.

 

[j toomey]

Just to follow back up for anyone looking at this later, my local garage trouble shot this for a couple days and finally found the culprit. I had a bad pin on the two wire pigtail connector on the alternator. They were able to fix it up as ram doesn't sell just the pigtail connector (amazon does however for $20). I appreciate the reply's and guidance and hope this is useful for someone else down the road.

 

[j toomey]

Do you have AlfaOBD and know how to use it? If not just stop right here.
You can not fix these vehicles without proper diagnostic equipment.

And no you can not drop in an ECM just like that, they also need to be matched to the vehicle.

Diagnostic is the key, should have been done before the first dollar was spent on hardware.

While I appreciate your reply, I do understand that ECM's are programmed for a specific vehicle and they CAN be ordered online coming preprogrammed to your specific vehicle and are effectively plug and play.

The code thrown based on the data (not enough to throw a CEL) was generator field/F terminal circuit high. The diagnostics on this code would 90% of the time lead to a bad alternator (a coil went bad).

 

[Timd32]

Thanks for following up on this, always glad to see a answer.

Good luck with the rest of your adventures.

 

[Tuesdak]

Connectors having trouble... Not easy or fun to find. That shop deserves a good review.