downstream o2 sensor affecting fuel trim

[nickmoS14]

hi, im a bit new to forums so bear with me. but i have a 95 s14 and the idiot who owned it before never put o2 sensors in with the exhaust(no cat) and im gettin the upstream one, but the harness for the down stream one is non existent.
A. is the down stream o2 only for catalyst health?
B. if so will i be able to run in closed loop without the downstrem o2 or will it turn on the mil and keep me in open loop.

[Beemer]

you could trick the computer by installing resisters. but you need to find the harness for it.

[WalkerTech]

Nick,

I am a product specialist with Walker Products, a manufacturer and worldwide distributor of oxygen sensors. It is a common misconception that downstream O2’s exist only to monitor the cat, as the upstream sensor must work with the downstream to determine the correct AFR. Cutting out the downstream O2’s on a vehicle, as has been done to yours, forces the vehicle to run in open loop mode. You would gain better gas mileage and engine health by installing the downstream O2’s.

I'm assuming you have the the 2.4L in your SX?

[nickmoS14]

Yes I do. And I looked under my car for the harness and could not
Find it. I just got my upstream (not installed yet) but this weekend I'm going to see if the harness is still in the ECM and just cut
Somewhere. But if not I'll have to find a harness or just use
Wires into the ECM and route it down there.

[mxexux]

Nick,

I am a product specialist with Walker Products, a manufacturer and worldwide distributor of oxygen sensors. It is a common misconception that downstream O2’s exist only to monitor the cat, as the upstream sensor must work with the downstream to determine the correct AFR. Cutting out the downstream O2’s on a vehicle, as has been done to yours, forces the vehicle to run in open loop mode. You would gain better gas mileage and engine health by installing the downstream O2’s.

I'm assuming you have the the 2.4L in your SX?

Why are you saying things that are not true?

OP, downstream O2 is ONLY for monitoring cat efficiency. The car will run in closed loop without the downstream sensor, BUT the MIL will still be on because it will sense O2 sensor voltage always low.

[mxexux]

.........................Double post

[nickmoS14]

i thought MIL light is only turned on with emissions stuff? or is itts only obd2? correct me if i wrong. and if i habe a mil light on then ill be in open loop.

[PureRush]

hi, im a bit new to forums so bear with me. but i have a 95 s14 and the idiot who owned it before never put o2 sensors in with the exhaust(no cat) and im gettin the upstream one, but the harness for the down stream one is non existent.
A. is the down stream o2 only for catalyst health?
B. if so will i be able to run in closed loop without the downstrem o2 or will it turn on the mil and keep me in open loop.

The downstream O2's only purpose is to make sure the cat is functioning. The upstream O2 is crucial to engine performance and without a doubt should be installed and conected to the PCM. I dont have secondaries in my 350z and I get a check engine light. In my 240 though, I only have an upstream O2. Depending on the year, KA24DE's can be either OBDI or OBDII. OBDI only has one O2 sensor and OBDII has two (one pre one post cat). The previous owner might have swapped an OBDI KA24DE into your 95 which came with OBDII stock. The downstream bung can be plugged up without affecting the engine performance or closed loop but you will have a check engine light.

if you have a KA24DE with OBDII

[s1kzenki]

im having the same issue, my downstream o2 sensor wires came off the o2 sensor. now i have to buy a new o2 sensor. but will the car bogg or fuel cut at low acceleration without that downstream o2 sensor? thanx.