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macawgumbo

Check Engine Light And Possible Causes?

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Could somebody clue me in as to the first things first list to do when troubleshooting this check engine light?

1998 Mazda 626 4-cylinder Auto

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The CEL is caused by the ECU not receiving proper readings from the various sensors. Your vehicle is an OBDII (On Board Diagnostic ver 2) compliant vehicle and you can take it to an Autozone and they will read the OBDII codes for free. Based on the code, it will give information as to how to start troubleshooting the problem. Some problems can trip the initial code and cascade other codes to appear. Once you get the code(s), you can repost back here for a solution.

Another handy item would be for you to get the Haynes manual for your vehicle. It has some good sections on DIY work and a chapter on the engine management system and the OBDII codes.

Hope this helps B)

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cover it with black electrical tape.

problem solved. :biggrin:

actually, i agree, take it to autozone and have them check it out, then come back here and we'll offer what help we can.

B)

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The following codes were given:

P0133 - Heated O2 Sensor Slow Response

P0420 - Catylic (sp?) system below threshold (Can't remember exact wording)

Guy said it was all attributed to the O2 sensor which is what I thought.

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If you are under 70 or 80,000 miles, Mazda is required to fix any emissions problems for free by Federal Law.

Otherwise, I'd try the 02 sensor first, then possibly a bad catalyst.

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If you're car is over the fed mandate for emissions and you need to change it yourself it is pretty easy.

There are two O2 sensors, the primary is located on the exhaust manifold and the secondary is located after the catalytic converter. The P0133 could be causing the P0420 to trip. Anyway if you replace the primary O2 sensor, you can borrow/rent the slotted socket from Autozone. They usually charge you the price for the socket and give a full refund when you return it...within one day. Be sure to use anti-seize compoung on the threads when installing the new O2 sensor.

Be sure to reset the ECU and clear the CEL after installation. This can be done either by disconnecting the neg battery cable, press the brake pedal for around 20 secs, and reattach the neg battery cable. If you have a factory radio with a security code, you'll need to reset the radio code. If you purchase the parts from Autozone, you may be able to go back there and have them reset the CEL with their ODBII reader/analyzer.

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It has about 64,000. So could I take it to the dealer and they will take care of it for free?

Yep. If they try to charge you any money for it tell them you'll go call the EPA and shut that place down :angry:

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