The check machine light, that yellow or red light that scares most drivers to death is certainly a very good thing to see. The check machine light is a warning expedient that comes on when your car has a qoute with the emissions operate system.
In this report I want to post you of some of the top five Codes connected to the check machine 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 describe failure or fault in the vehicles volatile Emissions theory 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 machine 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 efficiency, but a code in the 300 series that is not repaired instantly will cause a code 420.
#4 Codes 171,172,174
This series of codes are the Oxygen Sensors telling the Computer what fuel combination 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 0.00 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 person troubleshoot the Egr theory 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 machine light does come on don't turn the oil, won't help, don't panic that won't help either.
What will help is having a pro 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.