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Thread: Missing O2 wiring
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09-15-2006 #1
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Missing O2 wiring
I am in the final stages of modifying the wiring harness for a '96 LT1 and came across a head scratcher. According to the wiring diagram, OBDII LT1s use four O2 sensors (two before and two after cat). I could only find three (two right, one left), so took a look at the PCM pins. Low and behold, there never was a fourth O2 sensor on this engine. Is this normal?
Now, if I stick with three, where do I place the third one? On a crossover pipe? Maybe have two the the right side? As I am not running a cat, how far apart should they be. I was tempted to remove it, but I have read that the purpose of four was better sensing and, therefore, economy. The other option would be to wire in the fourth O2 sensor.
Any advice or pearls of wisdom?
Brent
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09-20-2006 #2
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NO NO NO
have the reaar o2 removed from the computer via LS1edit
the reaar 02 was there ONLY to monitor cat efficiency
If you remove it and do not edit the computer to not look for it then you will have the check eng light on and the car wont go into closed loop. In wich case you fuel maps and timing maps will be pulled back for safety nor will the car read the front 02's to maintain proper air fuel ratios.
you can also get possibly and 02 simulator for that spot
also the reason you only have threee is because it was a two into one exaust with one cat.
hope this helps
Ken F69 Camaro
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09-21-2006 #3
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If your engine came from a car that had a single cat, there will be only 3 O2 sensors-2 front and 1 behind the cat. With dual cats, there will be 4 sensors-2 front and one behind each of the two cats.
As I'm sure you already know, you will want to keep the two upstream O2 sensors. The only reason for the rear sensor is to monitor the efficiency of the cat.
If you are not using a cat, there is no reason for the rear sensor and it will generate codes and other problems. Edit it out or use a simulator for the reasons Madspeed mentioned.
09-25-2006 #4
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Thanks guys, I figured it the same way after I thought about it awhile :-) I was going to run a simulator, but was not keen on the extra wiring so decided to look into converting to a OBDI but have not heard back from MadZ28 site. However, I will look at the site you recommended. Thanks again.
Brent
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