Ok so I went over a bump and the jeep shut off and won't start up. I checked the codes and I'm gettin no crank signal.

 

looks like you have a 94? i believe they have whats called a CPS (crank position sensor) i wonder if it is to blame? the CPS determines the throttle controll, and if its like the TPS (throttle position sensor) on my 99 xj, then it controlls some tranny stuff too. idk too much about CPS's but but i think the ideas the same. from there... lets see... fuses are probably out as you said the code was the crank signal.... jeez, ill save wasting time here and deff. go w/ the CPS. BUT, if not, then make sure that all the components that lend to you "spark" are good... (you know, AIR, FUEL, SPARK...) good luck dude...

what kinda bump we talking???

 

A bump at some sand dunes, enough for the front ed to bottom out. Even driving on the road some times I would hit a little dip in the road and it would shut off for a second.

 

sounds like maybe the cps or more likely a loose battery terminal/ground. Check your battery holddown and the ground strap near the battery.

 

check the wiring to cps for brittle and cracked spot touching to ground causing shut down

 

Best to post the EXACT code number here, as with OBD, the devil is in the details.

Test your crank sensor.

If you aren't getting an input signal from that sensor to the computer, you will NOT have spark and you will not have fuel going TO the fuel injector (even though you may have good fuel pressure at the fuel rail).

 

First I get 12 then 11 and then the 55.

 

these guys are right..check the cps it should be on the top of your bell housing...if it's not that then definitely look at the negative wirse on the battery. it is even a good idea to add a second good negative wire from the battery to the body right there by the battery. i had this same issue & since i added the second ground wire no probs

 

Definitely check/repair/replace the battery terminals and battery ground first.

If problem persists, replace the CKPS

 

Does anybody know what each wire on the crank sensor does?

 

No but here's the testing procedure maybe you'll figure it out


TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines
1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (SEE Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.





TESTING PROCECURE for 1987 – 1990 4.0 L engines
Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If the CPS is out of that range by much, replace it.

Test # 2 - You will need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.

 

I'm not good with a meter. What would the setting look like and what kind of reading