So I have been fighting a charging issues since last year. Finally investing dome time into it. When the truck is cold I’m not charging and have no tach. As the truck warms up the tach eventually starts bouncing until it comes back on line along with normal charging. It will work perfect until shut down. The colder the day the longer it takes. I have checked all the pins on the PCM and it checks out per the stickie. I changed out the CPS just to rule that’s out. Still does the same thing only now once it starts charging the tach will peg out at 4K and come back to normal from there.
The wait to start light also does not come on when first starting as well. It will come on after the truck is running and then starts to flicker and go out once it starts charging. I have disconnected the grid heaters last year and nothing changed with the charging.
Would a bad intake temp sensor cause this? I’m going to browse the print now and start going thru everything again. Just looking for ideas or if anyone has had a odd charging issues like this.

 

I would check the grounds. Battery to chassis, engine to chassis. Take a good set of jumper cables hook both to battery negitive side, then hook other ends to the engine and the other to the chassis and see if that helps.

 

I am no electrical expert, but it kind of sounds like a heat/colt, expansion/contraction problem. Like when it is cold contraction is causing a bad connection and when hotter, expansion is connecting the fault, Just a theory based on my basic physics knowledge...Mark

 

I'm having similar issues oil pressure goes way low and volts show low when I first start when it is cold..if I hit the dash over the oil gauge it bounces up some which makes me think loose ground somewhere but now the key turns on all the dash lights but does not seem to have the last 1/4 inch spring back action when the starter is supposed to be activated by the key in the switch SO WON"T START..I was able to start by jumping a wire from battery to the starter brown wire off the 2 wire connection by the battery so I know the starter works fine...however when I tested the battery when it was running it only showed 12.15 or so and not the 12.7 I would expect if it was charging...
Some had said it might be the ignition switch itself that is not fully activating the alternator or starter relay but not to just throw parts at it till figure out which is the issue but not really sure HOW to test to see which could be..ANY help in figuring it out would be great and where to start at first.
TIA
PS last week it would not do anything to start and as soon as I put in a extra ground strap from engine to firewall it started right up but even without that it was charging at the normal 12-8-14.00 range which now is not.
Did you ever figure out what the issue was with yours?
TIA

 

A new used computer solved everything! Charging, tach and Wait to start works as advertised. Definitely follow the sticky on troubleshooting the no charging or other PCM issues. Check for power at the PCM. If I had to guess there was something going on with the Crank position sensor(which I changed and checked all the wiring back to the PCM. I’m getting the feeling these PCMs are nearing The end of life. I wouldn’t condemn one right away but it’s up on the list for me right with everything else. I’m going to see if they can repair mine so I have a spare.

 

That sounds like a bad ignition switch. I have had both the switch and tumbler break on mine in the past 12 years. They are fairly cheap and break often enough. Also check the harness to the cluster. It does not hurt to have extra grounds with the level of rust on some of these.