The check engine light, that yellow or red light that scares most drivers to death is actually 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.

In this Article I want to inform you of some of the
top five Codes related to the check engine light.

#1 I have to say would be the code PO300-PO310 this code is for a MISFIRE which can be any combination of spark plugs, plug wires, distributor cap coils or Fuel Injectors and even the PCM!

#2 Codes PO440,442

These codes represent failure or defect in the vehicles EVAPORATIVE EMISSIONS SYSTEM it keeps harmful fuel vapors from escaping into the atmosphere. This failure can range from a loose or defective Gas Cap or its 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 the rear O2 sensor is the one that monitors Catalytic Converter effeciency, but a code in the 300 series that is not repaired promptly will cause a code 420.

#4 Codes 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 IN THE MIXTURE) LEANER THAN 14.6to1 vacuum leaks,low fuel pressure plugged injectors, failed O2 sensor(s). Same thing For RICH Readings (more fuel than air) plugged air filter,bad coolant temp sensor,leaking fuel injectors, too high fuel pressure. Before you run out and 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

This code requires that someone troubleshoot the EGR System and on FORD the DPFE (backpressure Sensor) most EGR codes are due to carbon build-up in the EGR passages and NOT the EGR Valve.

But if the Check engine light does come on don't change the oil, 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 Yes it WILL COST MONEY and it will save you money too in fuel mileage.

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By Randy Harkins