Hey
I have an 05 Dakota 4.7 2WD with 99k and a rebuilt trans, on the freeway I get code P0203 accompanied by a bad misfire. I got this code about 2 years ago and replaced the injector and cleaned the connection and it seemed fine. Fast forward I got the code again while I was on the freeway, it misses pretty bad when I give her some gas. Any insight since the injector is relatively new? When I'm driving around town I don't get the code. PCM?

 

In the 2005 service manual for code P0203, in addition to the fuel injector and PCM being possible causes, it also lists the #3 injector circuit being open or shorted to ground, and the Auto Shutdown Relay/ASR circuit being open or shorted to ground. If it were me, I would visually inspect as much of the #3 injector wires/harness as I can for any damage. Also, if the injector was not an OEM part, but aftermarket, the injector itself may no longer be playing nice...even if relatively new. If you can't see anything wrong with the wiring and harness, I would probably try moving the injector to another cylinder and seeing if the code moves to that specific new cylinder (P0201, P0202, P0204, etc) after a period of time. If it does, you'll know it's the injector...and replace it with only OEM if applicable.