Q&A

 Master

P0304 is an engine misfire code on #4 cylinder. And code P0354 indicates a problem in the ignition coil circuit "D". How many miles on your truck? When was the last time you replaced the plugs and wires? The 100k tune-up is a myth in my opinion, I see lots of problems with plugs, wires and coils way before that mileage.

 Journeyman

this is an obd2 trouble table, it can help you understand the meaning of code.
http://chinasinoy.com/service/diagnostic-trouble-code-tab...
for p0354 the possible solution:
Short to voltage or ground on COP driver circuit
Open on COP driver circuit
Loose connection at coil or broken connector locks
Bad Coil (COP)
Faulty Powertrain Control Module
for the po304 the possible solution:
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
this tool can reset your car code.
http://chinasinoy.com/wholesale/launch-obd2-code-creader-...
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.