2001 xj 4.0 aw4 4wd


p0340
p1491
p0442
p1694
p0303
p0456

i know one of them is the fan relay "not working"
one is a misfire on cylinder 3
one is the camshaft sensor
and one a vaccum leak..

funny thing is sometimes i turn on the jeep and the check engine light is off and sometimes is on...jeep runs fine and is doing around 210 miles out the whole tank (city)

 

Sounds like some of those codes may be old stored codes. Disconnect your battery for about 2 minutes then reconnect it. This will clear the trouble codes out. So when and if you set another code, you know for sure the problem is there. The light won't come on unless a problem is occuring. That means that even if there are stored codes, the light won't come on unless a problem is happening.

 

p0340: Cam sensor
p1491: Rad. fan control relay circuit
p0442: Evap. Emission control system leak detected (medium leak)
p1694: No Bus messages between TCM and PCM
p0303: Cylinder #3 misfire
p0456: Evap. Emission control system leak detected (small leak)

 

I agree with clearing codes and seeing what returns.

Then attack those codes.

 

You can also clear them by removing the battery cables and holding them together away from the battery.
The codes also disappear after 50 key starts unless they reoccur.