O2 sensor volatage?
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Joined: Sep 2002
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From: Johnson Kansas
O2 sensor volatage?
I'm working on my 89. I'm not set up to scan yet--probably a winter project-- just built up a 383. I got to wondering if I could perhaps tell what the o2 readings are by using a high impedance voltmeter and checking the voltage on the o2 sensor. The fact that the o2 sensor runs off of one wire and a ground tells me it is likely to be analog. If so the computer more and likely feeds it a voltage through a pull down resistor and thus measures the voltage drop. Assuming so, the voltage would tell me what the O2 readings are if I had the figures to interpolate. Would anybody have those voltages and table to convert them to 02 aproximations. Is there a flaw in my logic? This might allow me to know if I can drive the car or had better leave it on the jackstands until I can burn a chip.
Thanks in advance.
Thanks in advance.
Drifting
Joined: Mar 1999
Posts: 1,931
Likes: 1
From: Norcross GA
Re: O2 sensor volatage? (Kendall)
Volt meter won't do yo much good.
You are correct in that the sensor is tied to the ECM through a voltage divider circuit, but that is just extraneous info.
The O2 is a narrow band unit. It is suppose to be switching from rail to rail. A voltmeter measures average voltage. What you would need is a scope.
But not really. If you set your ECM up in Diag mode (ALDL: A->B) After the codes flash, the ECM will go into a monitoring mode. The SES light will tell you if the ECM is seeing Rich or Lean condition. In closed loop, it should be continually flashing, with the On time = the Off time. This would be the neutral 14.7:1 point. When you go to WOT, the SES should come On, indicating a rich condition. SES ON = >14.7:1 SES OFF = <14.7:1
This should give you an indication of how far off your tuning is. Don't forget to read the plugs. The O2 is just a sensor. The plugs show the real thing.
You are correct in that the sensor is tied to the ECM through a voltage divider circuit, but that is just extraneous info.
The O2 is a narrow band unit. It is suppose to be switching from rail to rail. A voltmeter measures average voltage. What you would need is a scope.
But not really. If you set your ECM up in Diag mode (ALDL: A->B) After the codes flash, the ECM will go into a monitoring mode. The SES light will tell you if the ECM is seeing Rich or Lean condition. In closed loop, it should be continually flashing, with the On time = the Off time. This would be the neutral 14.7:1 point. When you go to WOT, the SES should come On, indicating a rich condition. SES ON = >14.7:1 SES OFF = <14.7:1
This should give you an indication of how far off your tuning is. Don't forget to read the plugs. The O2 is just a sensor. The plugs show the real thing.
