Headers/O2
 

Another longstanding problem that's been nagging me is my O2 sensor. Ever since I redid my exhaust I've had my cel for it.

That makes sense to me though, since I went from a stock non-CA setup to a cat delete 2 1/4" headers-back pipe. But I replaced the sensor at re time with a new denso one and the light still comes on. Is there any way to fix this without going back to the stock cat setup?

Maybe try putting an extension on the sensor. I used these on my IS300 aftermarket header. http://www.ebay.com/itm/161119594890...84.m1423.l2649

is this the ones with two 02 sensors? one before and one after? if so the spacers might actually do the trick.

Negative. I had one sensor after the cat before I swapped exhausts and the same thing after - just one sensor in the same spot (non California). My truck was sold new in Oregon.

Edit: Turbo I went ahead and got the spacers though. $9 free shipping what the heck. If they don't work I'll save them for when I put test pipes only car.

I just finished reading through this from the Massive Truck Info sticky at TN.

It seems like something is wrong because this document says that systems with a single sensor are mounted on the header area, which I have seen before. Systems with two sensors have the same first one have one in the headers and the second after the cat.

Mine has one sensor and it is after the cat. The headers are aftermarket pacesetters, which only allow for the one after the cat. Any insight?

O2 sensors run at a specific temp. Try moving it closer to exhaust ports.

That's exactly why I was worried. It said 750°F is when it kicks on - Do you know if this sensor is a heated sensor?

As far as moving it, that might be kinda tough. How would you suggest?

Since the stock location of the O2 sensor is ahead of the CAT there shouldn't be any reason for an O2 CEL just because you removed the CAT. I have had O2 sensor issues for 2 reasons:

1) Had a leaky exhaust ahead of the sensor allowing air (O2) in and causing bad readings.
2) Used some "sensor safe" sealant on the O2 sensor flange which had enough silicon in it to kill the O2 sensor.

Good luck!

Jim G.

Yeah, I'm tracking with you here. The fact that you only had one after the cat is a problem since it can't do it's job detecting the amount of oxygen after the cat. I don't know how it managed to run without throwing a CEL before, but now it is like it's supposed to with the new exhaust setup.

The first thing would be to figure out if you truck is a CA emissions vehicle, meaning it's supposed to have two O2 sensors. If it's not, then just move the O2 sensor before the cat and that'll fix it.

You're probably getting some crazy air/fuel ratios, I wouldn't be surprised if you're also running lean or rich.

What EXACTLY is the CEL telling you, as in what code do you receive?

I meant to post yesterday but you got to it first! Anyhow, I fixed it. Turns out the wiring was incorrect, with the b+ going to the sensor signal. I corrected the wiring using a couple posts I found and no more CEL.

Pulled codes and the knock sensor code is gone too - I think the ECM was reaching it's maximum capability of retarding the timing due to the O2 sensor not working. These two things fixed, my motor runs significantly better - sounds healthier, no more hesitation between 2900-3300 RPMs, and the exhaust is clean. (It was literally as putting out drips of water and my mileage was ~10 per gallon.)

Actually I found out the stock location on a non-CA sensor is behind the CAT. On CA-equipped models, there are two sensors and the one after the CAT is a "sub-sensor."

I think reason mine can be after the CAT and still be effective is because even though the O2 sensor doesn't switch on until it reaches 750°, the 4-wire sensor is equipped with a heater (whereas the earlier sensors are not.)

Glad to hear! I think I missed on the first read-through you deleted the cat, so yeah that's a non-factor. Having the O2 after the cat is just plain odd... unless they don't really care much about how the engine is performing and it's on there strickly for passing emissions. In some newer engines, O2s are placed on the headers in the engine bay, way before the cat.

Umm, nope.


Stock location on all 22R/RE engines with O2 is before the converter.
Some may have it in the manifold and some may have it in the downpipe or even just in front of the converter.

California started the mess requiring a 2nd O2 after the cat in order to verify the converter was working.

Codes were 21 O2 front circuit, 42 VSS, 52 knock sensor. Still have 42, pretty sure it's a connection issue. O2 and knock codes are gone now.

From what I've read this far, '94 non-CA (truck originally sold in Oregon/I have the papers from PO) had one 4-wire sensor after CAT only. This would make sense since when I redid the exhaust there was only one place for the sensor, which was after the CAT.

I'm no expert, but I know this truck pretty well and i can definitely say that in the case of the '94s, some things that are commonly written about for 22re's have been different for me. One example the speedometer issues folks commonly have - '94 has no speedo cable. I think this could be the same kind of thing here. If my truck is the only '94 non-CA with one O2 sensor after the CAT I'd love to hear from another user what they experience.

As far as the sensor placement there's a few things that don't add up for what your saying though...
- The stock header/exhaust assembly had only one sensor (I wasn't missing one) and it was after the cat. I pulled it out and replaced it. Saw it with my ow eyes.
- The replacement headers came with a CAT delete pipe and that pipe contains the only sensor flange. There is no other flange anywhere else.
- From a practical standpoint, I believe the heated sensor is the key. Personally any time I've seen a 22re sensor in the headers it hasn't been a 4-wire sensor, which makes sense because why would it need a heater to reach the desired operating temperature.

I do get your point about it sensing the exhaust after the CAT but then I don't know if the ECM accounts for that or not. I mean why couldn't it? Totally guessing but as long as there are no leaks before the sensor then why wouldn't it be to asses the exhaust as well as verify the CAT's working?

The point is the ECU cannot know if the cat does its job if it doesn't know what the cat was fed, and that would require a sensor in front of the cat, which is how the system was designed and should work- all should have the sensor ahead of the cat and some have another after the cat. (Sorry for the puns ;))


The ECU feeds air into the exhaust through the PAIR system, and this is after the combustion process has occurred. This extra air helps the converter catalyze hydrocarbons not oxidized within the engine in order to reduce CO and HC, and to an extent NOx, emissions.


The ECU cannot accurately control fuel mixture if it doesn't sample the exhaust before the cat.


Unless you can accurately claim to have owned the truck off the showroom floor, I'd bet a dollar against donuts that someone changed it. And the logical way of changing things around so the ECU doesn't freak out would be:
- install 22R header, which does not have O2;
- put the O2 sensor after the cat so the ECU doesn't complain.


That will keep the ECU happy and allow a person to tune the engine as well since the ECU won't be mucking with things if the converter does its job since the signal comes after the converter.