Steve lock

keep getting codes
p0340
po122
po456
po391
I already changed csps and fuel filter. car cap looks ok . when i reset the codes it comes up with p0340 fist but i have changed the crank shaft sensor 2 times. I'm lost

dave1123

Welcome to CF!

Check the wiring harness to the CPS for damage and good connections. You can also check the output for pulses. Check to see if the plugs on the PCM are loose or corroded. You can check for pulses by back-probing the connector, that is inserting a thin wire into the back side of the connector pins and using a multimeter. The CPS reads the starter gear teeth as an indication that the crankshaft is in fact turning.

94zj318

I can tell you P0456 is an emissions leak, my '02 4.0 WJ has the same code. When the PCM throws a P0456 code, it's likely to also throw the P0442 and P0455 codes as well (this according to my mechanic at the Jeep dealer), all of which indicate evap leaks, so check your hoses and take your Jeep to a mechanic to get an evap smoke test done on it to determine where the leak is, and fix it. I determined that I have a muffler leak with a small hole in the muffler, which explains the CEL (Check Engine Light). If you spray carb cleaner in the engine near the evap hoses while the Jeep is running, and the engine stumbles, you most likely have a leak somewhere around there.

You can Google the other codes, as the Onboard Diagnostics (OBD) II system uses universal codes for most things for all manufacturers, so you don't have to search far for those codes. (:

Good luck!