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Discussion Starter #1
So, I recently have been involved with the evil mistress P0171. I read out my O2 sensor feedbacks (voltage and AFR) and nailed it down to the pre-cat O2 sensor. After a call to Lotus of Pittsburgh ($250/sensor) and checking LotusGarage ($160/sensor) I finally came across a deal...$35ish/sensor from carjunky.com. I thought 'heck, at that price I'll just replace them both and be done with it'. WRONG.

CEL back within a block of my house. Checked codes...I'm getting P0135 and P0136 (both o2 sensor heater circuit malfunction). Now my question...The wiring for the sensors has Black, Grey, and two whites. I figured the white wires to be, essentially, the same. Is it possible they aren't (ie, if wired backwards could this be my P0135/6)? Voltage feedback on both sensors is flatlined (and doesn't change with load/rpm/speed/anything). I DIDN'T wire them wrong (black to black, grey to grey, white to white) - I'm sure I got that. I'm just trying to think of other things before looking at returning and getting the sensors from Lotus Garage...Ideas?

btw, STFT and LTFT look good. MAF sensor checked and clean (also compared resistance with a buddies' exige). DEF. something with the o2's.

Thanks Guys!!!
 

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Discussion Starter #2
Nothing? Anyone have the wiring diagram for the o2....what is black, gray, white, white??
 

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Discussion Starter #4
Did you ever get this fixed?
Get it figured out.
Yea, sorry, I should have posted. Anyway, I think the problem arose from crap o2 sensors. The sensor heaters didn't get to temp quick enough and threw the codes. I ended up buying sensors from lotusgarage...no problems since the install.
 

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Avoid the cheap chinese knockoff sensors. The ones I've seen frequently had heaters that were out of spec (incorrect resistance). If memory serves the ECU checks the current on the O2 heaters and decides to trip the code or not. The only difference between many 4 wire O2 sensors is merely the plug and wire length. Cutting and extending wires can be an option but be aware some sensors use SS wire and you can't solder it.

-Michael
 
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