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 Post subject: p0140 oxygen sensor?
PostPosted: Sat Mar 14, 2009 8:29 pm 
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Joined: Thu Jul 19, 2007 8:21 pm
Posts: 22
Location: Buffalo, NY
hey, i just got a 98 R/T coupe. When I bought it, the guy (neonmike, on here btw) let me know it needed a downstream o2 sensor and had the cel coming on and off and gave me a used one with the car that he said he got out the junkyard. So the car has been throwing code p0140 for the last couple of days and today I put the oxygen sensor he gave me in, Had to heat up the old one to get it out! and cleared the code with my little pocket scanner. I test drove the car to get some oil change stuff from Autozone. On the way it throws the code again. i scanned it and erased it and it came right back on. so i figured the o2 sensor he had got out the jy was trash, so i bought a new one from Advance on the way back, 65 bucks! :ireful: . Its a Bosch one that looks really different from the one that was on the car, but had the same plug so i figured it was good. I put it in and did my oil change and went for a ride. About five minutes on the highway and the cel came back on, i scanned it and it was the same p0140 i erased it and it came right back. What else to i need to check? do i need a converter? any input on how to keep the code off and from coming back would be great. Thanks! - Tony


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 Post subject: Re: p0140 oxygen sensor?
PostPosted: Sat Mar 14, 2009 10:36 pm 
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Joined: Mon Apr 21, 2008 3:59 pm
Posts: 3687
Location: F.L.-Aye
sucks to be out of 65 bucks, you should have grabbed another one from a JY first, or try to find someone who could get you a used one to test that was good. check your wiring harness for cracks and if its frayed.

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 Post subject: Re: p0140 oxygen sensor?
PostPosted: Sun Mar 15, 2009 12:13 am 
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Joined: Wed Sep 24, 2008 9:06 pm
Posts: 120
You should realize that maybe your O2 sensor is going off because something is causing it to. The sensor itself maybe fine.

neonlifer


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 Post subject: Re: p0140 oxygen sensor?
PostPosted: Sun Mar 15, 2009 1:08 am 
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Neon Mechanic
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Location: Phoenix, AZ it's quite hot outside. BUMMER!
Quote:
P0140 Downstream O2 Sensor Stays On At Center



hm. have you checked the wiring to the PCM?

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 Post subject: Re: p0140 oxygen sensor?
PostPosted: Sun Mar 15, 2009 7:34 am 
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Joined: Wed Dec 10, 2008 4:41 pm
Posts: 79
Location: Rochester Hills, Michigan
Mine set the same code over and over as yours does. Changed the sensor like you did and same problem. What I found on my 98 RT is the some of the wiring under the PDC had rubbed thru to the copper on the trans mount bracket on the frame rail. It was pretty packed in that area. I repaired the wiring, wrapped it in new tape and added some plastic wire cover (convalute (sp?)) and added a piece of foam rubber on top of the bracket. No more codes. One of the bad wires was for the AIS and one was for the heater circuit for the down stream O2.... but there are many wires in that bundle that could have been affected. Hope this helps.


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 Post subject: Re: p0140 oxygen sensor?
PostPosted: Sun Mar 15, 2009 8:22 am 
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Location: Northwest Wisconsin
P0140 usually (if it is not the sensor) is caused by either the sensor ground or signal wire having an open circuit. You should be able to find that with an ohmmeter. Check the TN/WT wire from the sensor connector to pin 51 at the PCM and the BK/LB wire from the sensor connector to ground. The TN/WT also goes through another connector C160 (Lt. Grey) near the PDC. If you can't find the break, try making an overlay harness by getting those wires from a junkyard harness. The O2 sensor connector can be disassembled. See the electrical connector how to in the Archived Posts forum.

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 Post subject: Re: p0140 oxygen sensor?
PostPosted: Sun Mar 15, 2009 11:47 pm 
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Joined: Thu Jul 19, 2007 8:21 pm
Posts: 22
Location: Buffalo, NY
Thanks for all the info guys. the car seems to be running fine with the cel on. I wont have time to check that wiring until next weekend. Is it going to damage anything to keep driving the car until then? Im going to have to be up under hood when i install the booger bushings i had just ordered from modern anyway next weekend. Thanks again for all the input guys, I really appreciate it. -Tony


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