Vehicle won't crank now.

[Warriorpluto]

Same thing happened to me. I was getting crazy voltages and low voltage like that. I assumed the worse and the thing still wouldn't crank after replaced all of the battery cables and the battery. Ended up being the starter. I felt dumb not checking it before ordering all kinds of stuff lol my truck only had 130k at the time so i figured the starter was good. I was wrong.

 

[Marlon Tomera]

This past Saturday I did remove the fuse box by use of the front and rear bails and looked for corrosion on all the terminals and then replaced it. We will tweak the positive and negative battery cables while my son in law tries to crank the engine over. There was no filter removed to gain access to the pressure switch. We are getting the code of U01-100 (Loss of Communications to the ECM/PCM). Could this be a security lockout issue? If it is, will we have to take the vehicle to the dealership so that they can hook up their computer to it and see what codes are showing up? We had to connect up some jumper cables from my truck to their battery, because it was dead. We had the cables on for about 20 minutes, then removed them and started troubleshooting, but then the battery drained down to about 5 VDC. Do you think that the battery is too weak and needs to be replaced?

Okay this past week I've been watching allot of Scanner Danner YouTube videos on how he troubleshoots these kind of symptoms. We had a week battery, so put it on the charger Friday and let it charge up. And Saturday Morning I checked the battery voltage and it was around 11.9 VDC, and I was wanting to check and see if I had a 5VDC reference circuit, and as soon as we turned to the key to the ON position, the voltage dropped to 5.8 VDC. So we connected up the jumper cables from another vehicle and had a good 12 VDC to work with. I did find that the 5 VDC Reference Circuit was working. And if I tested right and read the schematic right, the PCM/ECM isn't providing a signal or voltage to the Starter Relay, which in turn powers the starter fuses, So we have come to the conclusion that the PCM/ECM is bad. If anyone has any thoughts on this please let me know. Thanks for all the help guys and gals.

 

[kbuskill]

Your battery is no good... a 12 V battery should read 12.8 - 13.25 V after being on a charger overnight.

Remember the K.I.S.S. principal... Keep It Simple Stupid.... install a new battery before wasting money on an ECM.