Hello all!

I am having a perpetual slow oxygen sensor code on bank 1 sensor 1 by the header. I have a custom exhaust (Since the pacesetter downpipe rusted through) and the O2 bung was a custom job. My mechanic told me to try and see if I can convert the unheated oxygen sensor to a heated one. He said that the sensor isn't getting up to temperature since it is relocated further down the exhaust, and the heated sensor could potentially fix this.

Is it possible?

I know it can't be as easy as running a power wire down to a new harness and getting a new sensor...

Thanks,
Kevin

Heated sensor means just that. The faster the O2 sensor is heated up, the faster the car can into closed loop, and better gas mileage, and less emissions.

If you have a heater circuit code, either the heater in O2 sensor is shot, or your wiring for the heater has an open, you would need a wiring and see if you have 12V on the heater wire


- 2004 Cavalier - 124k, owned since new

Rob,

Maybe I was unclear, but the current O2 is the standard Unheated sensor. But since the relocation has moved it further away from the manifold, my mechanic believes that the sensor isn't getting warm enough so it is throwing a P0133 code of a Slow sensor. Not a bad sensor, but a slow one. There isn't a heater circuit code because it doesn't have one.

Thanks for the response!

I am running a turbocharged 2.4L with 2.5" exhaust no cat and straight through Magnaflow muffler on a 2002 Cavalier. The car takes about 10 minutes to warm up enough to go into closed loop. When the car goes into closed loop when it is cold it sounds like it wants to stall. The engine rpms go down to about 800 and then it catches itself. I have watched on a scanner what it is doing. As soon as it enters closed loop the Short Term Fuel Trims drop down to about -20 which is causing the problem and slowly climbs back up to the normal -4 to +4. Also if I go and take off without letting the car fully warm up it will hesitate in between shifts. Even with it fully warm it will hesitate a tiny little bit between shifts. The cause for this is the O2 sensor. When you modify an exhaust to make it flow better the O2 sensor does not reach the temperature it needs to. I have spent lots of money on buying the OEM O2 Sensors and this still did not fix it.

The solution to this problem is to install a Heated 4-wire O2 sensor in place of the stock 2-wire O2 Sensor.

This will work for anyone who is running a modified exhaust either N/A or Boosted.

I went out and bought a Universal Bosch 4-wire O2 Sensor Part # 15729 and wired it up. This cost me about $60 at the local parts store. You have to cut the factory O2 Sensor wires and use the plug off of it. The black wire on the new sensor is the signal wire. This gets attached to the Black wire on the factory sensor plug that you have cut off the sensor. The Gray wire on the new sensor gets attached to the gray wire on the factory sensor plug that you cut off the factory sensor. Now you must locate the plug for the rear O2 Sensor after the cat. There will be 2 brown wires on the harness side of the plug. On the other side of the plug these wires turn into 1 black and 1 brown. There is no polarity on these wires. Now you must attach both of the white wires from the new sensor to the 2 brown wires (I chose not to tap into the wires on the sensor side of the plug because it is a $170 sensor from GM).

I noticed a huge difference in thew way the fuel trims were acting right after the installation. They are so much closer and faster now. The car goes into Closed loop in under a minute when it is cold from sitting over night. And there is no more hesitation between shifts.

zedyred..

Thank you for your very detailed response! I have had the same problem with the revs dropping, and then the computer catching itself and firing them back up. I have also noted the hesitation that you have stated in your response, so it seems to me that this might be the answer!

I assume you chose to go to the wires for the rear heated sensor because you are 100% positive that they will only be hot when necessary? Is there an easy way to catch those brown wires in the engine compartment? It sounded like to ran the wires all the way back to the other O2 sensor. This seems odd to me, maybe I misunderstood?

Also, I have tried a Bosch O2 in my car before (trying to fix this problem earlier) and it was the worst thing I ever did....any thoughts?

Finally, how long have you had this setup? and did you have a check engine light before you completed this task? (I assume it took away the check engine if you did have one)

Thank you very much for the response...
Kevin

i have a 97 sunfire with no rear 02, anyone know where to wire in the heated sensor?


1991 Skyline GTR
1996 Sunfire

just type this in quick search , Heated O2 Sensor in Modified Exhaust Write Up - Performance Forum.


no i cleared the check engine light after i did this and 2 years i had not see it again.

Zedy,

Thanks again, I will do that search in the performance forum. This really seems like the answer.

Have a happy holiday!!

Kevin