I will be driving and my check engine comes on right after the truck feels like it slips out of gear. I don't loose power in the motor, it keeps idling. I have to put it in neutral then back in drive to keep driving. I had a friend read the codes and he said the following were listed PO121B, TPS Sense A range, PO234 Engine Over boost condition. He doesn't know alot about dodge. So he cleared the codes out on Monday June 16 and on Tues June 17 it happened again. If someone can tell me what the codes are and or tell me what I need to fix it.

99 dodge quad 4x4

Thank for any help
Mark
garrett2500