Check Engine Light – Top Five Most Common Trouble Codes and what they mean

Check Engine Light

Seeing a check engine light come on can scare most drivers, but it actually is a very good thing to see. The check engine light is a warning device that comes on when your vehicle has a problem with the emissions control system. The top five trouble codes are as follows.

1.) Code P0300-P0310 this code is for a misfire which can be any combination of spark plugs, plug wires, distributor cap coils of the fuel injectors and even the PCM.

2.)Code P0440,442 These codes represent failure or defect in the vehicles evaporative emissions system, it keeps harmful vapors from escaping into the atmosphere. This failure can range from a loose or defective gas cap or it's seal, to a leak in one of the plastic tubes that run from the fuel tank to the engine compartment and a charcoal canister where fuel vapors are stored.

3.)Code 420 is the code for a failed catalytic converter or O2 sensor which monitors the catalytic converters efficiency, but a code in the 300 series that is not repaired promptly will cause a code 420.

4.)Code 171,172,174 This series of codes are the oxygen sensors telling the computer what fuel mixture they see, some are LEAN (more air than fuel) leaner than 14.6 to 1 vacuum leaks, low fuel pressure, plugged injectors of failed O2 sensor (s). Same thing for RICH readings (more fuel than air) a plugged air filter, bad coolant temp sensor, leaking fuel injector or too high of fuel pressure. Before you run out a buy a $100.00 O2 sensor or two, test to make sure the O2 sensor can function, troubleshoot the fuel delivery/management system.

5.)EGR codes These codes requires that someone troubleshoot the EGR system and on a Ford the DPFE (back pressure sensor) most EGR codes are due to a carbon build-up in the EGR passages and not the EGR valve.

What will help is having a professional auto repair shop with an OBDII scan tool to diagnose your problem and fix it properly,which it turn saves money.

Articles that may be related to this one

• July 7, 2010 -- How to use an OBD-II scanner to diagnose engine problems
• February 5, 2010 -- Oxygen Sensors are Critical to passing Emissions Testing