What is the code for P0505?

Run an OBD code scanner or lookup what the code means. Don't always rely on the codes though.. they can be a red herring.

The service manual usually has information on the codes http://onlyrepairmanuals.com/downloads/nissan-pathfinder-repair-manual-1995-2005/

That code is for the idle speed control valve. Please follow the link P0505 Honda Idle Air Control Valve

P0505 14 ICS Malfunction
http://www.ericthecarguy.com/29-obd-codes/obd-ii-codes/honda-obd-ii-specific-codes/215-p0505-idle-air-control-valve-malfunction-honda

p0120 means you have a throtle position sensor problem could get expesive if throtle body is bad p0505 is same problem it means throtle idle controle valve problem hmm short bad ecm or bad throtle body hope this helps

P0505 - Idle Control System Malfunctionhttp://engine-codes.com/p0505.htmlForum CodePossible causes- IACV-AAC valve harness is open or shorted
- IACV-AAC valve poor electrical connection
- Faulty IACV-AAC valve

Read more: http://engine-codes.com/p0505.html#ixzz1zVJIt34L

P0505: Idle Air Control Valve System fault, Code P0505
-Vacuum leak
-Dirty throttle body
-IAC motor defective
-Poor electrical connection to the IAC valve, hope this helps and good-day !

This is an obd2 code trouble table, it can help you understand the meaning of code.
And for p0505, the possible solutions:
This should be a fairly straightforward diagnosis. Start by clearing the fault codes. Then unplug the IAC and start the engine (This may cause other IAC codes to set. Just ignore them for now). If the P0505 code doesn't reset, replace the IAC. It is internally shorting one of the IAC circuits. If the code DOES return after unplugging the IAC and starting the engine, then you know it isn't the IAC motor. Visually check the wiring harness all the way back to the PCM. You may need to visually inspect the harness by removing all the insulation off the wires. It is possible that the wires could be shorting to eachother or to other wires in the harness.
If there are no wiring problems, and the code keeps returning with the IAC unplugged, you can check the PCM by removing the IAC wires from the PCM connector (or clipping the wires in a location where they can be repaired easily) and then start the engine (If you're not sure, don't do it. Take it to a qualified professional). Now if the code doesn't reset there is a problem with the wiring. Check for continuity on all the IAC wires. Any resistance points to a problem. Check for voltage on any(At this point there shouldn't be any voltages on the wires because they're clipped at one end and unplugged at the IAC). Repair as necessary. But if the P0505 code DOES reset after removing the IAC wires from the PCM connector(or clipping them), replace the PCM, there's a problem internally on the IAC control circuit.
I know this tool can hekp you clear the code. hope help.

Its the IAC idle air contorll unit its on the air horn and controlls the air flow at idle This code is saying that something is malfunctioning it is not saying at what RPM it is happening at there is 5 or 6 differant codes for this and they run from P0505 thought P0509 but if you are geting P0505 i would just replace the unit but check the connection to it first it may be a bad connection it dose get weather and heat and that cerates problems with contacts

This should be a fairly straightforward diagnosis. Start by clearing the fault codes. Then unplug the IAC and start the engine (This may cause other IAC codes to set. Just ignore them for now). If the P0505 code doesn't reset, replace the IAC. It is internally shorting one of the IAC circuits. If the code DOES return after unplugging the IAC and starting the engine, then you know it isn't the IAC motor. Visually check the wiring harness all the way back to the PCM. You may need to visually inspect the harness by removing all the insulation off the wires. It is possible that the wires could be shorting to eachother or to other wires in the harness.

If there are no wiring problems, and the code keeps returning with the IAC unplugged, you can check the PCM by removing the IAC wires from the PCM connector (or clipping the wires in a location where they can be repaired easily) and then start the engine (If you're not sure, don't do it. Take it to a qualified professional). Now if the code doesn't reset there is a problem with the wiring. Check for continuity on all the IAC wires. Any resistance points to a problem. Check for voltage on any(At this point there shouldn't be any voltages on the wires because they're clipped at one end and unplugged at the IAC). Repair as necessary. But if the P0505 code DOES reset after removing the IAC wires from the PCM connector(or clipping them), replace the PCM, there's a problem internally on the IAC control circuit.

Around $200.00 for parts, labor and fees.

this code make reference to low idle engine,maybe the throttle body is dirty , air filter clogged, vacumm leak , pcv valve clogged, check for thoses