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Nov 12 07 9:31 AM

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I've been getting a P0140 code after driving for 10 to 15 minutes. (I've been reseting it) The car I bought got a new exhaust system before I bought it. New catalytic converter and all, but the O2 sensor is mounted after the catalytic converter. Shouldn't it be mounted before the catalytic converter? Just wondering if this may be part of my problem because the O2 sensor looks new. Anyone else repaired a P0140 code?

1997 Blue Aspire
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#4 [url]

Nov 14 07 4:42 PM

Yeah, the one in the exhaust pipe. I don't see one on the pipe coming down from the engine, the only one I have is one after my catalytic converter. Wondering if it has anything to do with the P0140 code I'm getting. My O2 sensor is new.


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Posts: 2,121

#5 [url]

Nov 14 07 6:42 PM

There's supposed to be two on some cars, I'm not sure which of our cars but my 97 aspire is a 2 oxy sensor car. The 1st one is located in front of the engine on the exhaust manifold down low, but before the down pipe. This is a "single" wire type. The second one is supposed to be right after the cat, (My car didn't have the exhaust system when I got it) but I have what's left of the wires. Speaking of wires, this second sensor is a "four" wire, heated type. It actually gets "pre" heated cause they aren't read till they reach about 600 degrees. I believe the purpose of that second one, is to sample exhaust AFTER the cat has had a chance to clean it up some......... Ok went out to the garage and got the book and the wiring diagrams say:
1988-89 festy (carb) 1 sensor w/ single wire
1989-93 festy (FI) 1 sensor w/ single wire
1994-95 aspire 1 sensor, single wire w/shield wire
1996-1997 aspire 1 sensor w/ single wire, and 1 sensor w/ 4 wires.
Sorry, don't have anything after that for our Aussi Gang.

The precision is the religion for me!

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Executive Member

Posts: 306

#6 [url]

Nov 14 07 10:16 PM

The first O2 sensor in the exhaust is the one in the manifold and the second is the one after the cat. The primary is the 1st one and is used by the engine to determine correct A/F (air/fuel) ratios for the motor. The secondary O2 sensor is the second one installed(after the cat) to monitor catalyst efficiency(how well the catalytic converter is working).

ALL 95 and OLDER cars will be a single O2 sensor setup. They only have the O2 sensor in the exhaust manifold.(OBD0, OBD1 and Some older cars didn't have OBD but were fuel injected) Almost every auto manufacturer before 96 had thier own scan tool type and connector type. This could vary depending on year as well.

ALL 96 and NEWER cars WILL have two O2 sensors. This is due to the implementation of OBD2(on board diagnostics 2). OBD2 was implemented to make a universal style connector for Shops and scan tools to connect, retreive codes and diagnose problems much easier.

This applies to ALL automobiles sold in the USA. Not just the Aspire. (not sure about our Aussie conterparts - Sorry guys.) Was the OBD2 standard excepted in AUS?)

PO140 - is a OBD2 code that states there is no activity on O2 sensor bank 1 sensor 2(the one after the cat).

Check to see if your O2 sensor after the cat has good CLEAN wiring - no cuts or shorts/broken wires. There are sensors that you can buy that are universal and require you to wire them into your stock wiring connector. They have a plastic box that is about 2"x1"x1" with four wires going in on both sides. This is a splice that comes with most BOSCH universal O2 sensors. If it is wired wrong it will throw this code. It is usually less expensive than the direct fit (prewired) sensor. Check to see if you have this spliced connector. If you do verify the connections in it and whether or not it is wired correctly.

The aspire's equipped with aftercat (secondary) O2's have a strange swoop in the pipe that angles the sensor so it does not hit the bottom of the shifter of the transmission. Some Mentally challenged individual installed a non secondary o2 sensor exhaust system in my secondary o2 sensor equipped car. They then welded a O2 bung(the nut that holds the O2 sensor in the pipe) straight up on top of the pipe. The O2 sensor was rubbing on the bottom of the shifter - It lasted about 4 days before the pipe vibrating back and forth rubbed through the secondary o2 sensor wires and shorted them. Could possibly be a similar problem for you?

Hope this helps.

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#7 [url]

Nov 16 07 1:09 PM

That helps! Okay, I found the one on the manifold. Smaller that I expected. Did find a plug down there for the second one but couldn't get it apart. Still need to get out the book and make sure its wired correctly. Need to find out the which colors are which on the O2 sensor. Its a universal 4 wire. And it is very close to the shift linkage but all the gears I tried never touched the wires.

Thanks for all the good info!!


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