FIND WHERE GROUND SLICE FOR CRANK AND CAM SHAFT SENSOR IS

1995 Jeep Grand Cherokee

Tiny

jeffinotown

July, 28, 2013 AT 10:51 AM

Having intermittent start problem, but now total failure. Getting no reading on ground wire for crank or camshaft sensor. Book says they splice together along with o2 and transmission speed sensor. I assume its related to a bad ground. But can't find splice or where they finally ground out. New crank sensor, coil, camshaft sensor, wire and plugs, not pcm, installed brand new on and same problem.I'm 90% sure its a bad ground, also tac jumps when running. Where is ground?

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Tiny

caradiodoc

July, 28, 2013 AT 12:00 PM

The sensor ground wires always go to ground through the Engine Computer so current can be monitored. You should find 0.2 volts on it. There will always be four ground wires on the computer. Two are sensor grounds and two are power grounds. By "power" grounds they mean high-power stuff like injectors and ignition coils that are pulsed on and off. If there is the slightest bit of resistance in those wires there will be a voltage drop each time one of those things fires. Those voltage drops are insignificant for those circuits but they would seriously interfere with the tiny changes in sensor voltage signals. That's why the low-power and highly precise sensors use their own ground wires.

Tiny

jeffinotown

July, 28, 2013 AT 2:14 PM

I started trying to trace all the ground wires back, I got to the right side of engine were the harness get huge, going to pcm, but wire started pulling sheathing off, so I stopped, I instead tried splicing at the primary hub on left side of engine, where 9 ground wires come together. I had 0 resistance on cps, cks, thottle, ect. So I tried to just slice and run a ground from there and see if I could get anything, but problem remains! Could it be the pcm itself? Or should I check the grounds on the pcm, and if so, I can find nothing online as to pin numbers to check the 4 grounds you mentioned. I figured all the wires are good to that one hub, there are 2 wires going back tward the pcm, but then 2 more appear on the other side of block, and after trying to pry appart, and having wire breaking. I stopped right there, and tried just running a seperate ground off that hub! No luck

Tiny

caradiodoc

July, 28, 2013 AT 3:20 PM

I'm trying to find a service manual for your vehicle but not having any luck so far. The best I can tell you right now is to look for the same color wire you're tracing at the computer, then do the resistance check from that terminal in the computer's connector to the sensors. On most other Chrysler products that was a black wire with a blue tracer.

To add to the misery I'm heading on a road trip to Detroit, Ohio, and Indianapolis tonight and will be gone two or three days. I'll check on your progress when I get back. In the meantime I'll keep looking for a service manual. If you can find a copy of the manufacturer's manual, that will show where each splice is located on a drawing. The guys at the Chrysler dealership I used to work at were real happy to find that and make photocopies of the relevant pages for people, and they had the dealership owner's blessings to do that. If you pursue that, look for a Jeep dealership. We didn't have the Jeep franchise so we didn't have service manuals specific to them.

Tiny

jeffinotown

July, 28, 2013 AT 4:23 PM

Where is the primary ground for everything? Sensors, pcm the whole kit and kubudle?I know this is a ground issue, where does everything ground out, especially the crank or cam, does it run threw the pcm to ground? And if so, where? I'm getting no spark on alll brand new parts that were working till today! Thank you SO much for the help, on a Sunday! Thank you!

Tiny

caradiodoc

July, 28, 2013 AT 8:38 PM

I never needed to find the grounds but I'm pretty sure the wires come out of the harness and are bolted to the inner fender near the head light or firewall.

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