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Re: Replaced O2 sensor, now check engine light on! Posted by Ari [Email] ![]() ![]() In Reply to: Replaced O2 sensor, now check engine light on!, Geza in CA, Thu, 23 Jan 2003 16:05:28 Members do not see ads below this line. - Help Keep This Site Online - Signup |
It helps to know what is causing the Check Engine light. Just about any fault in the engine drives the light, not just the O2 sensor. And frankly, even an O2 sensor fault doesn't mean the sensor is bad.
If the sensor is stuck rich or stuck lean, you'll get an O2 sensor fault, and the CE light will come on. But if your engine happens to be running lean because of a vacuum leak, or rich because of a bad Fuel Pressure Regulator, the O2 sensor will be stuck lean or rich, but will be telling the truth. Replacing a perfectly good sensor won't fix the problem. It's possible the old sensor was marginal, and the new sensor is only reporting more truly.
Step one is to determine why the CE Light is on. See if you can get the Engine Control fault codes read out. As pointed out above, don't just assume that they are telling you what part to replace. Pull the spark plugs and see if you're running rich or lean. Check for vacuum leaks.
The fault codes will help narrow it down. There are so many things that can trigger the CE light...
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