what is the process for testing the alternator without removing it?
Talked to the guy i returned the ficm to and he says that he plugged in that ficm i returned into another truck and it ran fine which makes me think its my PCM but thats just my guess. its not the original PCM in the truck either i had to replace a couple years ago when i had a no crank issue. took weeks to check the electrical system to find out it was the PCM... man that was a rough time! kinda coming to the same conclusions unless there is something im not checking.

 

Yeah Mark, with diode issues you can see normal to elevated DC voltages. If you put a voltmeter across the battery terminal or alternator output and frame, turn the meter to read AC, you can see how much AC is present. It will change with the load as well.

A couple of graphs I'm using in a vid. Most alternators can have a 0.25v AC ripple, some up to 0.5v. But others 0.5v can be normal and 1.0v for bad. It's best to view on an scope rather than a meter. What that doesn't seem like much, the frequency is what can get some things and the DC voltage might be up over 15v. Good electronics will have a design so this does not affect its circuits, but .........

 

since i am not in a running situation, can i conduct a test between the alternators positive terminal and the body to check for any AC ripple larger than 0.5v while cranking? otherwise ill just pull it and take it to get tested.

 

Just another observation. FICM Logic Power still dropping to 9.5 volts when cranking is not good.

 

Wasn't there another thread ......

 

does that indicate a bad ficm?
I am going out tomorrow to get the alternator tested and another ficm from this guy. im affrraid to plug it in and have the same issue happen.

 

just wanna mention i never saw any voltage over 13v when it was running, i had the main voltage being monitored on the scanguage.

 

both were tested and came back ok. i dont see it being the batteries. ill swap them out too with another set if you think they could be an issue.

 

How about posting some images of the battery terminals?

While the OBD2 reports lower by about 0.5 volts on some channels, I've had no problem showing 13.8v and above.

Edit - have you ever changed the FICM relay?

 

i will post some pics tomorrow!
have not changed the relay, I hear it clicking and get .60 when testing its resistance. not sure what it should be. I may change that out too for sake of it being bad unless that reading is good.

 

Your batteries are not okay. Maybe you put some dead/weak batteries in your truck?. The low volts at startup will fry your FICM. Also check the wiring and the connections on batteries and frame. Use jumper cables (only for testing) and connect the batteries and (just to see if the volts go up) install additional cables in addition to the existing battery wiring.

Use a FICM from a truck that is running and watch out for the better volts.

 

Can you click it? Then you'll know the injectors are engaged

 

Take the FICM's that you believe might be bad and install them on your friends truck... That will tell you if they are bad or not. It doesn't fix your problem, but when you do fix the problem you'll know that you have a good FICM ready to go.

 

i get no click at all when doing the injector self test

 

did not have time today to work on the truck gonna be getting things done tomorrow!