3rd Gen Ram - Charging Issues - Could be a BAD TIPM Ground!

[EricKBattleGround]

My 2006 Ram 2500 has been - figuratively - eating a set of batteries every 2 years. I have the 5.9 Cummins, and the problem invariably is noticed when the PASSENGER side battery boils over and causes a mess.

I recently had the same issue crop up - and made a very surprising discovery. The TIPM ground on the driver's side fender COULD be the cause of a number of charging issues! NOT ALL OF THEM, of course - a failed alternator or bad battery will NOT fall into this category. This likely applies equally to diesel- and gasoline-engined trucks.

Technically, there's two TIPM ground connections: G104 is a bolted ground near the driver's side battery negative post, and G106 is a bolted ground closer to the windshield on the driver's side. It turns out that the G106 ground has up to 16 different possible connections on the vehicle, yet it has NO copper cable return to battery negative. (Pictures now attached to help identify the grounds.)

TLDR summary: unbolt and clean the G106 ground connection - applying a thin coat of GREASE to the threads of the bolt. Better yet - add an 8 AWG ground (same size as the cable going to G104) from this connection to the battery negative post.

Longer technical discussion and history follows
My truck has gone through 4 alternators (2 new, 2 reman) and 6 sets of batteries since 2012, with 2 alternator replacements and 4 sets of batteries since 2017. Every time I've had a failure, the passenger side battery is overcharged and the acid has boiled over.

A 2023 over-charging incident actually melted the lead off of the battery cable clamp in the crossover positive cable used with dual-battery installations, so I replaced it with a "sort of fits" part - correct length but the wrong cable end to bolt to the driver's side battery positive cable. I also installed a brand-new Bosch alternator.

In 2024, I replaced the batteries in my truck in March after yet another over-charging incident. I put in a set of AGM - absorbed glass mat - batteries as I'm tired of doing the "sulfuric acid cleanup on aisle 2" schtick. In October, I was less than 2 miles from my house when the voltmeter gauge was reading below 11 volts. At the time, I had an electric trailer brake controller that confirmed "battery voltage" of 10.79 volts. (That poor controller released its smoke genie when I reconnected grounds...giving me another fun troubleshooting issue.)

During initial diagnosis, I noted battery voltages were 13.2 volts on the passenger side and 12.4 volts on the driver side when measured with a multimeter. (Former) colleagues would likely tell me that I should have replaced both batteries. I took the "they're only 5 months in service" approach - and started thinking, why is the voltmeter gauge wrong when the battery still has a reasonable voltage?

I spent about 2 days reviewing the Dodge workshop manual - especially wiring diagrams. When I realized that the voltmeter gauge gets its reading from a CAN message from the TIPM, I started looking at the locations of the grounds in the engine compartment, and things "clicked" for me - a resistive ground connection (i.e., corrosion) on G106 could cause the TIPM to "see" a different voltage from the rest of the vehicle. I unbolted the G106 connection, cleaned the bolt and ring terminal, bolted everything back together - and the charging system operates normally!

Although cleaning the ground connection provided a fix, I was actually in the process of replacing all the battery cables with an aftermarket set. I had an additional 26" long cable built to connect from the driver's side battery negative to the G106 ground location. Since the bolt holding the G106 ground is potentially exposed, I would rather have a copper return path.

From an electronics integration perspective, I don't think it matters if you have a gas engine or a diesel engine. I think it is actually the TIPM's voltage reading that is normally driving the ECM to request charging. The TIPM's voltage reading is already on the CAN databus and is used by the instrument cluster for the voltmeter gauge; and the same CAN databus is connected to the engine ECM, whether it's an ECM for a gas engine or a diesel engine. So why not use the CAN message that's already there as the primary driver for battery charging?

If that last part seems speculative...well...consider that the TIPM in these trucks was derived from Mercedes passenger car and/or van applications and was already doing voltage monitoring for the cluster - therefore, it would be cheaper for DaimlerChrysler's Chrysler division to dictate software development requirements ("turn on this output when this value is received") than to develop duplicate circuitry.

 

[RTHudson]

Hey Eric, I'm in Vancouver, we might be neighbors. Anyway I have been having some unusual electrical issues with my 2018 3500. It began with an occasional failure to remote start, with the message "REMOTE START DISABLED". Then using the key to start, after the preheat cycle, the engine might or might not start. At first I thought it must be the batteries, they were five years old, so I replaced them. I still have the same issue, you switch on, wait for preheat and try a start. Usually there's a clunk sound, like a solenoid pulling in, and nothing happens. But sometimes if I switch off and wait a minute, and try again, the engine will turn over. But usually I have to use a jump pack to get a start. Is there a battery voltage monitoring system that might be disabling the start sequence? The alternator and batteries check good, is it possible there is leakage current drawing down voltage enough to cause this problem? Or maybe even a ground issue?

 

[EricKBattleGround]

I apologize - I missed this reply. I've been dealing with home repairs since late November and that's kept me off the forum.

There's been about 3 generations of electronic controls changes between the third gen Rams and 2018. That includes engine ECMs (at least 3 generations) as well as the TIPM. I can provide educated guesses about what the computers are doing, however, this is a case where studying the factory workshop manual for the starting system wiring might likely reveal more clues.

Since the problem has developed over time, a ground that is starting to corrode is far more likely. Certainly not the only cause. From my last 3 working years, though, grounds were the overlooked problem source more frequently when dealing with starting systems.

The difference between a remote start system like this and a more traditional starting system is how the ignition "key" is handled. I use quotes because a lot of cars have transitioned to pushbuttons. Basically, the key is now an input to a computer algorithm - and that algorithm can be modified to look for a key or a signal from a remote keyless entry (RKE) system.

The key question is whether or not the remote start algorithm is using the exact same inputs to determine that it's OK to crank the engine. If the remote start is requiring no vehicle motion, then it could be looking at the transmission data as well as data from all 4 wheel ends to decide that it's OK to start. (And a clue here is - if you can stop and then restart the engine from the driver's seat with the truck moving, the answer is likely "yes, the remote start algorithm is looking for no motion.")

Those are the thoughts I have at the moment. Sorry about the very delayed reply.

P.S. Testing how the starting system works is not something that should be done on a public street with any amount of traffic. One wrong move could cause an incident or accident. There's a reason that the stunts in TV advertisements say "DO NOT ATTEMPT. PROFESSIONAL DRIVER ON CLOSED COURSE." and I have actually encountered some of those professional drivers and closed courses out in Oregon.