MIL's 3500 6.7 Dies Intermittently

[lute]

MIL's truck has problems. Began with starter making a metallic grinding sound. Checked flex plate, nothing wrong there. Brought starter to Advance. Counter man tested both the old starter and a new one and they appeared identical in performance. But he very kindly gave me a new starter.
Installed it and it worked perfect with no grinding.
Next day drove to store, shut it off, restarted perfect 30 minutes later. Driving home engine died at stop light. Restarted after turning over longer than usual. Two miles later died again. This time no crank at all for 10 attempts although dash lights normal. Called tow truck, tried another 10 attempts, truck finally started and ran perfect for the 5 miles to home.
Re-tightened starter and battery connections. Batteries are 6 month old 1000 CA Interstates, voltage at 12.6. Voltage at starter with key on is 12.4. No CEL but scan comes up with U0141 lost communication to FCM.
The truck has an Edge tune.
Any ideas as to what could be causing the shutdowns?

 

[Dennis Shellito]

If the truck never had this problem before the starter swap I believe there is a wire connection that is not sound. I think you need to go over the wiring to the starter very carefully, and maybe crawl under the truck while it is running and move the wires to see if the engine dies. I find it hard to believe that the truck would have a whole different problem that soon, and I don't trust coincidences very much.

 

[lute]

You were absolutely correct.
Checked and rechecked connections.
Negative clamp could not be twisted with one hand, but using two hands it would rotate. Re-tightened and the truck is running great.
Many thanks for the diagnosis!

 

[lute]

Well, the no crank problem returned after two weeks of starting and running perfect.
Gear indicator lights have stopped working.
When drivers door is opened, the mileage indicator lights up with no key in the ignition.
When key is turned, the digital clock on the radio goes out.
Do these symptoms point anywhere?

 

[Dennis Shellito]

The first place I would start is the batteries, because bad batteries can cause weird anomalies. I would remove the batteries and then zip tie the positive cables to the negatives and then have the batteries load tested, not just voltage tested. If the batteries are more than a couple two or three years old I would replace them and not bother with testing. The cable ends need to be grounded for 30 minutes to reset anything that might have gone wonky from bad batteries. Please post your your results either way.

 

[lute]

Batteries checked out. Found what may be the problem and will start a new thread.
Thanks