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Old 01-05-2009, 10:26 AM   #1
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Default Random Check Engine Light

Been having some issues lately with the check engine light coming on while driving (usally longer distances 30+ mile on the hwy; sometimes in town but rarely). My first guess is the o2 sensor as the wire fell aganist the downpipe and melted so naturally the car would kick the light on after a while of seeing nothing. I've since replace the sensor with a new one (still a one wire; autozone bosch $15-$20) and extended new wire up to the CAS. Since the check engine light doesn't come on every drive but seems to randomly and stay on until the car is shut off and restarted.

Anyone have any idea? Possibly not the o2 sensor and something else? Possibly the wire used to replace the burn wire isn't good enough for the job?

Note: Car has a stock greddy kit with an intercooler and a bipes for some car background. Doubt any of that has to do with the issue but figure I would leave the info anyways.
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Old 01-05-2009, 11:19 AM   #2
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You dont have an OBD reader?

Check engine lights dont only come on because of faulty o2 sensors. It can be misfires, malfunctioning air meters, IAC valves, anything. **** they come on from running to rich as well.
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Old 01-05-2009, 11:28 AM   #3
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Since you're OBD1, you can just do the paper clip trick on your diagnostic box and it will tell you what code it is.

To do this, you have to jump the pin (sorry, can't remember which one) to ground and then turn the key to on position. The CEL will blink the code to you, and then you can search for that code online.
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Old 01-05-2009, 12:28 PM   #4
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Sometimes mine comes on randomly, but I think its because of running rich when cold. To tell you the truth I really dont care anymore, all the stock ecu controls is the fans, idle, and a/c anyway...
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Old 01-05-2009, 02:23 PM   #5
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Originally Posted by Cpt_Slow View Post
To do this, you have to jump the pin (sorry, can't remember which one) to ground and then turn the key to on position.
It's TEN. You jump that pin to ground, turn the key on, and count the blinks of the CEL to get the code. Here are the codes: Miata Computer Diagnostic Fault Codes
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