I've only had my TJ for a couple days but the engine light came on.  I've never worked with a Jeep engine before so I have no idea what's wrong.  It doesn't seem to be running bad, so I thought mabe it would just be something simple.  Any ideas what I should look at, like I said never worked with these engines.  

turn the key on an off a few times till it displayes the codes on the odometer... if any post em.

you can also unhook the battery cable and rehook em after a minute to reset it. I'd guess something to do with a o2 sensor maybe  

Ok the code is (P0340) anyone know the code system  

ya, I use google, I think ftgiles has em all memorized!

without looking it up I think its the camshaft position sensor, check out the connection on the passenger side on the oil pump driver which would be a distributor if it were an old cj  

Noooo... I don't have them memorized. I look them up...

P0340 is telling you that the Cam Shaft Position Sensor is not within range. Maybe it's a bad wire, a loose connector or the sensor is bad.  

you guys are fast. ok where is that located and how expensive is it to replace.  are you sure you don't have them memorized. lol  

What year is your TJ. In 2000 the 4.0L changed to be distributorless and it is on the passenger side of the block right above the motor mount. Previous to 2000 it is under the distributor cap. (Same location)  

2002 Sahara.  Yeah I was looking under the hood and couldn't find the distributor, I thought I was going nuts or something.  That explains it, I'm not going nuts after all.  

mudb8-:
ya, I use google, I think ftgiles has em all memorized!

without looking it up I think its the camshaft position sensor, check out the connection on the passenger side on the oil pump driver which would be a distributor if it were an old cj

LOL...  

Duh!!! I didn't even see that the first time.  Now I feel dumb. lol  Thanks for the help.  

so how important is the cam position sensor?  Do I have to replace it or can I leave it?  What exactly is it even for?  

Very important. The cam position sensor is how the PCM knows which cylinder is being fired. The crank position sensor only indicates piston position, but does not indicate if it's a compression stroke or an exhaust stroke.

The cam position sensor helps to control individule injectors at idle and low speed.

Mis-fires are detected by the crank position sensor. But, it is the cam position sensor that allows the PCM to know which cylinder is mis-firing. This information is important in order for the PCM to make minor adjustments to fuel injector pulse widths as indicated by the o2 sensors. If the adjustments don't bring things inline, then a trouble code gets thrown.  

well i fiddled with the wires and the engine light went off, so i guess we're good.  on another note how does the engine work without a distributor and plug wires.  i've never heard of a system like that, call me old fashioned.  

It's called coil-on-plug or COP.

The coil packs are sitting directly on each spark plug. So, no need for wires.

The PCM controls each coil separately. So, no need for a distributor.

Most COP systems use one coil for each plug. But The 4.0L only has 3 coils. The cool thing about the 4.0L design is that it fires two plugs at a time. One plug is in a cylinder on the compression stroke and the other plug is in a cylinder on the exhaust stroke.

This gives a little spark to the out going gasses to help burn any unused fuel. This helps with emissions and lowers exhuast gas tempatures, which plongs the life and effectivness of the catalytic converters.  

well that makes sense. i like it.