Does anybody know what these two codes really mean and what do I need to do to fix the problem.They are P0380 and P0121.thanks

 

P0380 Glow Plug/Heater Curcuit "A"

You got a problem with the relays the control the grid heaters

P0121 Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance Problem

APPS (Accelerator Pedal Position Sensor) sensor problem. Try reseting it first. If the doesn't work then replace it.

This procedure has shown to help 24 valve ISB engines. It is basically teaching the fly by wire accelerator on these trucks to reread the position of the pedal and it's limits. Most complaints this will help with is poor acceleration, improper shifting, bucking in 5 and 6 speeds. Has been known to increase fuel mileage in some instances.

1. Set parking brake
2. Disconnect negative battery cables on both batteries
3. Turn ignition key to run(to drain any remaining capacitors)
4. Let truck sit for 30 minutes( this is the recommended minimum)
5. Return ignition to OFF position
6. Reconnect both batteries and secure, not a timed event
7. Turn key to run position(not start) and depress accelerator pedal slowly all the way to the floor
8. Allow pedal to return to top position slowly
9. Turn ignition switch OFF
10.Release parking brake