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Re: O2 sensor question Posted by Ari [Email] ![]() ![]() In Reply to: O2 sensor question, 94 Aero, Thu, 23 Aug 2001 21:00:48 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The O2 sensor doesn't produce a signal until it gets to about 200 degrees C. The main purpose of the pre-heat, as I understand it, is to 'light-off' the sensor sooner. This reduces emissions when the engine is cold.
When the O2 sensor isn't operational, the engine control uses just the AMM to schedule fuel. Once the O2 sensor starts producing a signal, the control uses the AMM to get a coarse estimate of fuel, and the O2 sensor to fine tune the fuel delivery.
No emissions test that I know of tests cold emissions, and the impact on the environment is between you and your own personal demons. BUT - the engine control is assuming a heated sensor. It's going to expect an O2 sensor signal after some (short) period of time. If it doesn't see it, it'll continue to use the AMM signal. The Engine control also does diagnostics on the sensors, and if it doesn't see an O2 signal after some ?? minutes, it's going to flag the O2 sensor as bad and turn on the Check Engine light.
Now, here's the question - will an unheated sensor warm up from the exhaust gas stream before the Engine Control flags it as bad? That I can't say - I don't know the fault logic in the EC, and how fast the O2 sensor warms up depends on your driving. It may not be a problem at all, or a non-heated sensor will turn on the Check Engine light. Just a possiblity.
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