i have a 1989 gmc r3500 with a 454 that giving me a code DTC - 44.i believe that means its the oxygen sensor and something about being lean.i know it aint the fuel pump because i checked fuel pressure.what else could give me that code or is it probably mean i need t o replace the o2 sensor

also just wondering is there any difence between the o2 sensors w ith the plugs or the one with the wire connectors

If its the lean code, there is most likely a vacuum leak. Try the carb cleaner test

ok will do.i just got under my truck and i found out i actually dont have any o2 sensors.is that why im getting that code

well i found the o2 sensor it was in the back.and i found out my vac line to the egr valve had a hole in it.

thanks for updating your fix