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Re: Ari, need your input on 2-wire O2 Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 19 Oct 2006 08:15:52
In Reply to: Ari, need your input on 2-wire O2, KevinM, Wed, 18 Oct 2006 21:07:16 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Yes, in a two wire sensor, one wire is for the heater, and the other is the O2 signal. The body of the sensor is the ground reference for the signal, and the path for the current from the heater. Not ideal - that's why in later cars they went to 3 and 4 wire sensors - separate the high current heater from the sensor circuit, and no longer use the body for ground. But that doesn't matter on your car.
Yes, a reading of 25mv would indicate lean running. If the sensor was bad and indicating lean, that would cause the engine control to make the engine run rich.
The proper way to measure is not between the leads. For the signal wire (black), measure the voltage to ground. If you want to measure resistance, you should (1) measure to ground, not the other wire, and (2) unplug the connector, so you are measuring the sensor, not the sensor in parallel with the circuitry inside the ECU. For an O2 sensor, the unplugged resistance with the engine off should be in the many megohm range.
The O2 sensor controls about 25% of the fuel flow; the AMM controls 100%. So yes, the O2 sensor doesn't control as much as the AMM, but 25% is still quite a bit and can cause rich running.
posted by 192.249....
, Thu, 19 Oct 2006 08:15:52 <-- Viewing This Message
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