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oxygen sensor bypass/simulator

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Forum Name: Miscellaneous - Off Topic
Forum Discription: Topics that just don't fit anywhere else.
Printed Date: February 27, 2021 at 9:08 AM

Topic: oxygen sensor bypass/simulator

Posted By: beatnbronco
Subject: oxygen sensor bypass/simulator
Date Posted: April 17, 2010 at 10:50 AM

I'm sure this isn't the forum for this topic but i'm at an end. I have a 1995 Ford Bronco(full-size). I bought the truck and the check engine light is always on. When i had a diagnostic ran, come to find out the factory catalytic converter has been removed and there is no O2 sensor. I would like to find a bypass or simulator(whatever it's called) so that it tricks my ECU into thinking the catalytic converter is working properly and the check engine light won't stay on. I've searched ebay and google to no end, even tried but everytime i try to contact them i get an error so that I can locate the right part. Can someone give me some direction. Thanks for any and all help


Posted By: KPierson
Date Posted: April 17, 2010 at 11:06 AM

You may try contacting - from memory they do quite a bit of O2 simulators.

If you can determine how your OEM sensors work you may be able to build your own simulators cheap.  There are some older ones that output a voltage but most of the newer ones output a frequency.

Kevin Pierson

Posted By: beatnbronco
Date Posted: April 17, 2010 at 1:57 PM

real good place to start..thanks

Posted By: oldspark
Date Posted: April 17, 2010 at 7:29 PM
Corrected 19Apr10:

Just supply 450mV (narrowband) or 2.5V (wideband) depending on the O2 sensor.
Systems with O2 sensors target a ~14.7:1 mixture which is usually about half the voltage range of the sensor.

Your engine with thus think it's running perfect no matter how much smoke it puts out the back, or how big the holes in your pistons are.

Posted By: oldspark
Date Posted: April 18, 2010 at 11:37 PM
BUMP to highlight correction 19Apr10 to last reply:

The usual O2-Sensor output voltages are:
Narrowband = 450mV
Wideband = 2500mV

Posted By: beatnbronco
Date Posted: April 19, 2010 at 7:54 AM

hey oldspark..i don't know that much about electrical circuits..could you possibly tell me where to run a wire from and which one of the pins to hook it to on the sensor pigtail..sorry but i'm not sure enough about my experience to go messing with my electrical system on my truck..i'll crawl under my truck and look at the wire colors and try to figure it out and find out the voltage for my sensor

Posted By: oldspark
Date Posted: April 19, 2010 at 9:40 AM
I'd suggest you replace the 02 sensor if it's supposed to be fitted - it's probably the only way the ECU keeps its tune. Like I said - you could blow holes i your pistons of it leans out (at high revs etc).

I know nothing of the Bronco EMS/ECU & wiring.

Posted By: beatnbronco
Date Posted: April 19, 2010 at 11:14 AM
let's say i drill a hole in my exhaust and weld a nut fitted for the O2 sensor and install a new O2 sensor. will that correct my check engine light even if there is no catalytic converter? i considered doin it before just been busy and would like to know first before i attempt it..thanks for the help by the way

Posted By: awdeclipse
Date Posted: April 19, 2010 at 11:57 AM
If memory serves me well, in 1995 there was no active diagnosis of the catalytic converter. Most likely just fitting the 02 sensor in the exhaust will set a different fault. Now most likely you are setting an electrical fault if the sensor is not there.

If it helps, my friend had a 1998 Dodge Dakota with the cats removed and all he did was hang the 02 sensors in "open air" and he never set the check engine light. Putting them in the exhaust stream is more likely to set the fault then leaving them open air. Open air would allow the sensors to see excess oxygen at least instead of all the unconverted hydrocarbons.

Posted By: beatnbronco
Date Posted: April 19, 2010 at 2:53 PM
sounds better..ill give that a try..thx

Posted By: oldspark
Date Posted: April 19, 2010 at 4:26 PM
I agree the cat shouldn't be needed - except to prevent lung decomposition.

But see about fitting the sensor properly. It will mean better fuel economy - as Awd wrote, free air will make the ECU think there is more O2 than HC, therefore it will increase the fuel injected (watch for black smoke, splugs etc).
But at least it won't hole your pistons!

Posted By: KPierson
Date Posted: April 19, 2010 at 4:49 PM

Do you know if the O2 was before or after the cat?  If it was after it was most likely just to monitor the effectiveness of the cat and wouldn't effect engine management.  If it was precat then the removal of the cat wouldn't effect the O2.

Be careful mounting an O2 sensor in free air - wideband sensors have heaters and need air blown across them to keep them from failing.  I'm not sure about narrow band.

Kevin Pierson

Posted By: beatnbronco
Date Posted: April 19, 2010 at 5:15 PM

there was only 1 sensor and it was before the cat

Posted By: KPierson
Date Posted: April 19, 2010 at 7:08 PM

You should be able to replace it and the cat shouldn't matter at all since you are metering air before it.

As OldSpark mentioned it may improve fuel encomy.  It's possible that the vehicle is running rich right now to account for the lack of a closed loop fueling system.

Kevin Pierson

Posted By: oldspark
Date Posted: April 19, 2010 at 7:44 PM

AFAIK, older vehicles (1990s) didn't have cat checks.
And I'm not sure if the post-cat checks were O2 sensors - but I see cats more as removers of corrosive HS gases and other pollutants (NOx etc).

Certainly wideband sensors are a recent development way after the mid 1990s. (Or am I confusing the 1890s again?)

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