I have a 94 manual 4.0l cherokee. I shut it off the other day and then no spark. I have narrowed it down to no 8volt supply from the pcm. I just don't know why. After disconnecting the speed sensor, distributer, and crank position sensor, still no 8volt supply. Continuity through the circuit. Not grounded out. I even tried my pcm in another cherokee and it worked fine. I'm at a loss. Any suggestions?
I replaced coil and after a code p0335 the crank position sensor. The 8 volts comes from the pcm. I'm not getting it even after unplugging the crank, came, and speed sensor. Thought it might be grounded somewhere but it isn't.
I would check for the 8 volts at the pcm and trace the wires to the crank shaft sensor for an open or short. I listed trouble trees to your vehicle to help you diagnosis the problem. The Jeep has been known to have bad crank sensors, if all checks out it may still be possible to have a bad crank sensor.
Images from Alldata information website.
I have gone through that whole book. I have the schematic too. It's not shorted. Has continuity from pcm through all three cam,crank,speed sensor. Something is telling the pcm to not supply the 8 volts. I just don't know what it could be
Does your Jeep have a security system?
I did some research on this and if you use the remote to unlock the door, lock the door then unlock the door this resets the system. See if this changes things.
If the remotes don't work then turn the key on then go to the passenger door and lock and unlock the door three times.
Some security systems shut down the fuel infectors and some do the ignition system. I can't find any information on your system.
It's worth a shot.
I am also confused but am still looking. I am asking the administrator for more information.
When I saw that I was hoping that was it too. But mine does not have electric locks. The only wires going into the door is speaker wires. I do have the wires off the pcm that go to ccd + and ccd -
I don't know where they go from there though.
I have also tracked down the asd circuit. It all works except while cranking it over I only get 7 volts to the coil but if I use my scan tool and actuate the asd relay I get 12. My Chrysler book says I'm supposed to have 10 volts on that circuit but I have 12. Not sure why but even after jumping the relay it still has no affect on my 8 volts side of the cps.
The ASD relay does not supply voltage to Crank, Cam, or VSS.
Have you confirmed the 8 volts not coming from the PCM by back probing terminal 7 with the ignition on?
If no voltage there, confirm battery and ignition 12 volts going into the PCM at terminals 3 and 9.
Also confirm good grounds at terminals 11, 12, and 5,
No voltage pin 7. Yes 3,9. All grounds are good.
Finally took it to the shop. They saw the same thing. Owner said it's common problem. His tech line says to put a resister and ignition 12 volts to pin 7. Bringing it down to 8 volts. They did and it fired right up. So I guess no one knows why it happens.
That's kinda a "hot wire" fix. Still a fault preventing 8volts from the PCM at terminal 7. But if it works, it works...
My next suggestion would be checking the "pin fit" at terminal 7. Sometimes the female terminal in the connector get's widened preventing a good connection with the male terminal in the PCM. Should also inspect for any sign of corrosion.
Glad you got it going!