I replaced my crank sensor because i thought that was what was wrong. I posted about it earlier, but it was pretty broad. Ive basically narrowed it down to a fault between the CS and coil. The PCM surely isn't bad because I can read old codes, see new ones pop up if i remove relays, and it is giving juice and ground to the CS. It seems like something is just "off". It beats me.

 

How did you determine it wasn't switching the coil?

 

Test light to wires hooked up to neg- on battery. Did so individually. On the constant voltage, the initial voltage I assume was 12 volts, and then turned off after a short duration. As I started to turn it over, the test light turned back on, but more dimly. (Maybe battery too weak to supply voltage on top of starter draw?) Eitherway, im getting juice.

The other wire ( I cant remember green or black) did nothing. The way I understand it, i should be getting a (5v?) pulse as the flywheel passes the CS, but I had nothing, even a glow. To ensure it wasn't just me, I hooked up a new spark wire to directly to the coil and then to a brand new spark plug. I used jumper cable to get ground to the threads on the plug. No spark. I know this will work if it was working, as I have done it multiple times with success to test spark. Maybe I am doing the testing wrong for that wire? I found how online, but you know how everything is true on the internet...Im not exactly sure how the AC waveform works with the CS, so i could simply be doing it wrong.

 

Put your test light across the pins on the coil connector. Pull the fuel pump relay so your aren't flooding the cylinders.

PCM fires the coil by opening the ground side of the circuit. (coil fires when magnetic fields created by current flow collapse, when the circuit is broken) One wire is constant power, (controlled by ASD relay, that's why it goes away after three seconds) other wire is the ground wire going to the PCM.

 

I see, surely i didn't fry my PCM from shorting out the grounding...I didn't have it hooked up though, so it really shouldn't have done anything. Ill try that. Maybe it is the coil and Im getting flustered over nothing...

 

Nah, I don't think you hurt anything. Give it a shot, see what happens, let us know.

 

How about informing us again so we have an idea what's going on. What year truck? Any codes?
You need a signal from both the crank and cam sensor or you will not get a spark. If you put your test lead on the return wire to the pcm(#3) you will see the pulse when you turn the crank. The crank sensor doesn't get 12 volts!!! One ground wire, 5. volt feed and the return signal wire. The asd relay supplies 12 v (+) to the coil. Ditch the test light and get a meter to see voltage differences/readings.

 

Well, its pretty irrelevant now...I got it fixed! (Thank you HeyYou for the info about testing the input voltage to coil) I hooked up test light to wires on coil connector and it flashed as it is suppose to. Went to town, got a new coil, installed, and it fired right up. Runs better than it has for along time. Hard to tell if the CS helped any at all, but I know the coil did.

BTW Moparite, its a 1999 dodge ram 1500 sport 5.9L. Would like to change that 5.9L V8 to a 5.9L L6 but anyways.

 

Coolness. You have a truck again.