Engine wil only run when key is held in start position

the code should start with a p not hr, i think you just read how many hours the engine has run for. just turn key on and off 3 times third time leave it in run position this will display the codes. dont touch the trip button.

You may have a bad ignition switch If it does it it when the key is released. If held in position the vehicle stays running replace the ignition switch.

I don't quite understand what you mean by be held on. Normally you "hold on" to the key to start it and let it go back to the on position. If you have to hold the key on (start position) then you can might not be starting. The starter is turning the engine, but the engine not running? What happens when you give it gas?

try spraying some carb cleaner into a vaccum hose and see if it will run. If so then you have ignition but no fuel delivery. If not then you have an ignition problem. make sure you hear the fuel pump hum when you turn the key to the run position. It should run for +/- 5 seconds then shut off. remove gas cap and listen for fuel pump operation through the fill hole. If you can hear the pump then you have a fuel injection issue. If the engine starts and runs for a few seconds then shuts off then you can suspect the crank or cam position sensor. The fuel pump runs through the oil pressure switch which could also be an issue.

Are you able to start the truck with application of the gas pedal?

its one of two faults a starter fault or a switch fault,,
test the switch by hooking a wire to the small terminil on the starter and hooking a 12 volt light bulb up to it,,,now turn the key,,this bulb will light up,,,only for the time the key is held in the start up poshion if it stayes light up when you have let go the key the key switch if faulty

Check battery terminals are clean and firmly connected.

Check the transmission neutral interlock switch operation is OK.
Check +12V is appearing on the starter solenoid control wire when the ignition switch is held in the 'start' position.

If above ok, apply +12v directly to the starter solenoid activation control -starter should immediately engage.
If it doesn't run, you likely have a faulty starter motor.

try replacing the ignition barrel sounds like the ignition swith is goosed.

See if your security light is flashing if it is leave key in the on position untill light stops flashing then attempt to start you may have to repeat this two or three times

The engine computer turns on the fuel pump for 3 seconds when you turn the key to "ON".
If the engine does not start, the pump will not run.
When you turn the key to "Start", the fuel pump runs all the time the key is held in start.
When you turn the key on, it actiavtes the power relay, which provides power to the PCM or engine computer.
The PCM then activates the fuel pump relay, sending power to the fuel pump.
You should have one wire with 12V for 3 seconds in "run" position. This comes from the fuel pump relay to the inertia switch in the trunk and then to the fuel pump.
You should have one ground wire. black
One wire going to the fuel guage.
You may have another ground iwre ging to a diode before going to ground.

check cables to battery.if battery is 5years or older replace.
a bad ground cable and a weak battery will cause the starter to do as stated.