Just putting this information out there, hopefully it can help somebody!

My truck had voltage fluctuations and spikes, sometimes the voltage would spike to 15.5v for short periods. The problem would only appear at 2000 rpm, the headlights would flicker slightly. Occasionally a generic CEL(ECM power) would appear. I checked my camper and trailer batteries and wiring but they were OK. I replaced the batteries, then the alternator and then the TIPM, but the problem remained and I was seriously frustrated! In desperation, I removed and completely cleaned the ALL the battery cables and connections and the problem was finally fixed after 2 years! Now I have a solid charging system, and a bunch of new parts that probably weren't necessary. Lesson learned: clean all your charging system connections periodically!

 

No, wrong lesson learned. The correct lesson is that there is no substitute for correct troubleshooting. Arbitrary parts exchange is expensive and foolish at best. If you don't know, find someone that does. It is always less expensive.

 

Hey genius, thanks for stating the obvious, you know what they say about opinions, they are like a-holes because everyone has one!

 

True, but what I've stated is also true and you have paid the price. There is a fellow that just posted here about an abrupt engine failure asking for guesses as to what happened. Yet, he is there not us, made no tests, has zero information and accepting best guesses here. Without knowing what he's doing could and most likely will, cause more damage. There is a time, when it is more economical to go to someone there that is a professional. It is less expensive and your story here is a great example of what not to do.

 

Intermittent problems are the most difficult to diagnose and repair. Give the guy a break, he did what was necessary to fix the problem.

Now I would have a problem if it was a shop that just changed parts costing a customer big bucks for no relief.

 

I think we can keep it civil, can't we?

I have also seen professionals do the same hunt and peck for an intermittent problem..............

 

You know what? Your advice to go to talk to a pro really adds no value here. That kind of advice belongs in a ladies self-help forum. I put my experience here to really help others and to provide some meaningful information for anyone who has at least a basic understanding of electronics. One of the first steps in the electrical troubleshooting guide was to "THROROGHLY CLEAN ALL CONNECTIONS" regardless of the measured resistance, and that was where I made my error (I'm human, just like a professional). If you like, we can start a long discussion about the relationship between resistance, current and voltage, and how difficult it can be to detect/predict issues when corrosion is a factor. I'm sure there is formula for corrosive states somewhere but it's just easier to clean your charging systems connections periodically!

 

Colin, we can add no value to the OP without meaningful data. This can only occur if the OP knows what data to look for and how to seek it. Otherwise any contribution we make is nothing more than a guess. Over the years on this forum, we have seen the same thing over and over again. I actually thank the OP for bringing his experience to the fore. It is an example of poor troubleshooting. Many of us here know that under no circumstance should there be a voltage difference between batteries, but without stating this to the forum, correct advice could not be given. In the case of the abrupt engine failure, continued attempts to start the engine can cause severe damage. In that case, advice from this forum that allows that is just wrong. It is very important that any member that asks for help in this forum or any other forum, applies a reality test to any advice received. This is forum of users and enthusiasts. Very few members here are professional mechanics and any advice received must be screened accordingly. That is not to say that other folks experiences expressed here has no value, it does. Shotgunning parts exchange is stupid and expensive. That is the value of this thread.

 

Good troubleshooting of the charging system starts from here.

 

Wow, talk about a crapshow of a thread - good info followed up by a bunch of nonsense! There never was a measured voltage difference between the batteries, nor was there an abrupt engine failure like Steve said.

 

Yep, we need to keep this thread on topic or it will get cleaned up and reminders sent.

 

This is my first post in three years. Thanks colinP for your post good information. The reason I dont look at this Web site much anymore is because of people like Steve-I.

 

When the charging system and batteries perform as designed and all the system connections are good then BOTH BATTERIES should have the SAME VOLTAGE readings.
Different voltage readings are caused by bad cable connection.
Alternator outputs charging current to passenger side battery first then to driver side battery through the crossover cable. ECM monitors the driver side battery voltage only and this voltage is used to determine the alternator charging output. If the connection between the the two batteries is bad then the diver side battery would be undercharged and the passenger side battery would overcharged.
Monitoring the voltage of the two batteries is the easiest way to detect charging system problem.

 

Steve-I's post was kinda harsh but I'm sure that was not his intent...

 

There is a temp sensor underneath the driver side battery. It's used to determine the battery temp and control battery charging rate.
Wouldn't be surprise to see 15.5V charging voltage in COLD/FREEZING ambient temp.

Whatever voltage you see was the driver side battery voltage.
ECM has no clue what the passenger side battery voltage was.