Disclaimer: The information in this site is provided to you as a free service. We strive at CheckEngineCode.com to have the most current and accurate information. CheckEngineCode.com and its creators assume no responsibility for the accuracy or inaccuracy of the information provided.


Trouble Codes


The check engine light, that yellow-colored or reddish light that frightens many drivers to death is in fact an excellent thing. The check engine light is alerting gadget that gets triggered when a car suffers from issues in its emissions control system.

The most important and frequent codes related to the trouble codes are:

  • Codes PO300-PO310

    This code signals a MISFIRE which may be any mixture of fuel injectors, plug cables, spark plugs, provider cap coils or the PCM!

  • Codes PO440,442

    These specific codes suggest malfunction or defect in the cars evaporative pollutions system that stops dangerous fuel vapors from getting out into the atmosphere. This problem can vary from a loosened or maybe faulty gas cap or its seal, to a leak in one of the plastic-type pipes that operate from the tank to the motor area along with a charcoal bottle in which fuel vapors are accumulated.

  • Code 420

    Is the code for unsuccessful catalytic converter. The back oxygen detector is the one that watches catalytic converter performance, however a code in the 300 group which is not fixed immediately provokes a code 420.

  • Codes 171,172,174

    This series are the oxygen detectors informing the computer system of exactly what fuel combination they notice. Information provided can be: greater air level compared to fuel in the mixture, vacuum leaks, low fuel pressure, plugged injectors, failed oxygen sensor/s, more fuel than air, bad coolant temp sensor, leaking fuel injectors, too high fuel pressure. Before you run out and buy a $100.00 sensor test to make sure the oxygen sensor can function, troubleshoot the fuel delivery system.

  • 5 EGR codes

    This code requires that someone troubleshoot the EGR system and backpressure sensor most EGR codes are due to carbon build-up in the EGR passages and not the EGR valve.

If the Check engine light does come on don't change the oil, it won't help. don't panic that won't help either. What will help is having a professional with an OBDII scan tool diagnose your symptoms and fix it properly. It will cost money but it will save you money in fuel mileage.