What does code PO123 means?

SOURCE: what are these codes po123 and po121

These two codes are pointing at your TPS.
Your car may have a rough or high idle, or it could be surging or stumbling when accelerating and decelerating

The causes could be any of the following:
Your TPS may not be secured properly
You could have a short in the wiring to your TPS
The connectors to your TPS may be loose
Your TPS may be bad

Mike Butler

• 6674 Answers
• Posted on Jan 31, 2009

SOURCE: have trouble code po135 on a mitsubishi eclipse,

Oxygen sensor. try this link & scroll down until you find your codes.

http://www.troublecodes.net/mitsu/

SOURCE: 2005 pt cruiser check engine light came on

P0457 is a loose gas cap, P0456 is a small evap system leak. The seal on your gas cap is probably worn. Replace the cap, clear the codes with either a diagnostic tester or by disconnecting the battery for a few minutes and reconnecting it. It will take a few days for the code to come back if it isn't fixed, but that usually does the trick. I hope this helps.

SOURCE: code from computer; PO456

gas cap is probably a little loose. or a small leak somewere in tank vent system

SOURCE: CODES PO456 AND PO431 ANY QUICK FIX HERE

Quick fix? No... you probably knew that already.

A code P0431 may mean that one or more of the following has happened:
The catalytic converter is no longer functioning properly
An oxygen sensor is not reading (functioning) properly
There is an exhaust leak

Solution:
Inspect for exhaust leaks. Next step is to measure the voltage at the oxygen sensor on Bank 2. In fact, it would be a good idea to test each oxygen O2 sensor while you're at it.

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.

Usually this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running could conceivable cause this code as well or if the cap wasn't properly tightened. Any of the following could also be the cause:

A small leak in any of the EVAP hoses or fuel tank hoses
A small leak in the purge valve or vent valve
The EVAP Canister may be leaking

Solution:
First, using a scan tool activate the vent solenoid, sealing the system. Then monitor the fuel tank pressure (FTP) sensor. If the system is sealing properly, the number will stay consistent. If is isn't, the pressure sensor will show that as well. If the system slowly leaks, use a smoke machine and watch for smoke exiting the system at any EVAP component. Any where there is smoke exiting the system, that is the faulty component. Do not pressurize the EVAP system with air pressure. Doing so can damage the purge and vent solenoids in the system.