Started a new post from my previous post on truck shutting off while pulling a trailer. I have since narrowed it down to just the truck I BELIEVE. Quick refresher the truck shut off on me last weekend while pulling my camper. The battery light flickered along with other dash lights then the truck just shut off. Luckily I was able to pull over and after pushing the start button 5-10 times it finally start. Every time I hit the start button all light would turn off like the battery was completely dead. So it finally started I checked the batteries both batteries were at 12.6 and while started they were at 14.6 all wires were tight at batteries and starter. Fast forward to today went out to start it and nothing just a faint click. I checked both batteries and they were at 12.4-12.6 (plenty to start). So I disconnected both batteries for about 20 minutes to hopefully "clear" any issues. Reconnected batteries and it started right up like there were no issues. I turned it off hit the button and it fired back up. Went to Autozone to get some coolant came out. Nothing! Finally after hitting the push button 5-10 times it started. Got home turned off the truck tried to restart nothing. Disconnected batteries for 20 minutes reconnected and it started. LOL. **** is frustrating. Any ideas? Thanks all!!

 

When you tested the batteries, were they disconnected? You have to disconnect them to test them properly.

 

I had the negative cable off when I tested them. Of course I didn't load test them though. I'm fairly certain that it's not the batteries cause once it cranks over it cranks over like the day I bought it. Nice and strong.

 

My guess is something is shorting out. A dealer can find the problem so much faster by running a wiring diag than you can on your own.

 

Maybe try posting in the 6.7 board. All truck owners over there. Might take a while to get someone to weigh in.

 

It's either a battery/cable issue or the PCM. Chances it's the PCM; small. When you push the start button (or turn the key) you are offering a suggestion to the PCM that you'd like to start the engine. The PCM does that if all of its parameters are in line. Unless you have been in a nuclear blast and suffered an electromagnetic pulse, the PCM is probably fine. You haven't been in a nuclear blast, have you? Okay, so probably not the PCM, then.

Batteries can suffer a shorted cell that doesn't present itself constantly. To know that is the issue, you'd have to monitor battery voltage. It appears you have done that at least once in the failure. But you don't get any system warnings and a shorted cell even when just running would trigger a charge system light.

So, that pretty much leaves you with a problem with a cable. This can be internal corrosion or a bad connection in the primary cable. That would be my guess since you can get a click but no starter spin. That means the wire to trigger the solenoid seems to be functioning. A good test of the primary cable is to connect a DVOM to the cable to measure voltage drop. The positive end of the meter goes to the battery positive battery post -not the terminal but the post itself, the negative end goes to where the battery cable attaches to the starter stud -again, not the terminal, but the stud itself. When the cable is energized, you read the meter. If the meter reads zero or close to it, that means the cable is passing full voltage. If the meter reads voltage, then you know you have resistance through a voltage drop. Resistance can be caused by corrosion or a loose terminal, or even a damaged cable. You also have to test the primary ground since a fault in the ground is the same as a fault in the positive.

Also, you don't have to wait 20 minutes when you disconnect the battery to affect a computer reset. If you remove the negative terminal and press on the brake pedal a couple times, you will deplete the capacitor that provides power to store computer memory. But I think you fiddling with the cables is the thing that is helping to restore a connection.

 

I would also just check the ground connection on the block, lots of weird things happen due to grounding issues. Could be corrosion, or even a loose ground connection.

when you push the start button multiple times does anything happen each time? If nothing happens, then the PCM could be the culprit.

could also be that the truck loses track of the key, try putting the key fob in the receptacle under the storage tray in the console, that bypasses the usual electronic connection, if for instance the key battery is going dead.

 

Thanks for all the suggestions I really appreciate it. I set up an appointment to drop off Monday morning but will check the grounds on the block beforehand. Thanks all and I will report back with the diagnosis.