Rear O2 Sensor Extension Cable

[99SUS SFD]

I'm trying to find an extension cable for my rear O2 sensor. I thought I had purchased the right one but I was wrong.

Would I be better off buying a new harness? Which would I buy, CARB or Federal spec?

Thanks.

[Huffer]

Federal spec is the longer harness, and has the cats spaced apart, with the 2nd cat (and rear O2 sensor) is closer to the midpipe.
CARB has the two cats close together, right by the header.

You have a CARB spec exhaust, so when you install a high-flow cat (like Stromung or Random Tech) you need to extend the rear O2 harness to reach the rear O2 hole.

OR

you could just splice in some additional wire to extend the harness yourself

[99SUS SFD]

That's right, I kept confusing CARB and Federal spec. I'd like to get a solid connection rather than splicing wires myself. If I went to an auto parts store, and bought a Federal spec O2 harness (that would normally be an OEM replacement), I'd be all set wouldn't I?

The shop left the O2 sensor plugged into the exhaust, but the cable is open and I'd like to seal it up ASAP.

[decke48]

i believe theres a seperate harness that extends to the o2 plug (you can buy from the dealer). or you could buy a generic 4 wire o2 extension harness

[99SUS SFD]

Well that's what I bought. Huffer had given me a link to one he found, I spent $65 on it, and the shop said it wasn't the right one.

I'll see if a dealer has one I guess. Maybe NAPA will too.

[decke48]

i thought that was a 04 harness? because the universal ones only cost $25

[99SUS SFD]

Yeah it was from an '04 Impreza 2.5RS. His asking price was $50 plus $15 for shipping. If this one will work I don't care about the cost, I just don't want to be out the $65 plus have to find another one.

Maybe the shop doesn't know what they're talking about or didn't even try it? I'm going to crawl underneath it myself tonight and double check.

[Huffer]

The plug ends might be different...

[99SUS SFD]

Well that doesn't matter any more. I just plugged the extension into the male end by the motor, and it seemed to fit, but the cable is no where near long enough to reach the O2 sensor. Looks like a cut and splice job will be in order.

[decke48]

04 rs and 99 sus share the same rear o2 plug and wire length. wierd its short? the o2 wires are 17" and the harness must be 24"

[99SUS SFD]

I think if my car was Federal spec my original harness would be longer and therefore the extension would probably work. But I need a good 36" anyway before it'll reach. I recall seeing a universal extension that was 36" I believe...

[99SUS SFD]

Here's an update on this. I bought new O2 sensors hoping they'd have a bit longer harness coming off the sensor itself. Nope, same length. So I bought a 4 plug "universal" 36" extension harness from Summit. Doesn't fit.

I emailed a local Subaru dealer to see if they have an extension cable but they don't.

I don't know what to do. I spliced in my own extension wires but am still throwing a CEL, I think I may have reversed some wires. Instead of doing that again with the new sensor, I'd like to try and find a permanent solution.

[Huffer]

Have you tried installing the mechanical spacer on the Rear O2?

Also - IIRC it's pretty difficult to splice the wrong wires - the rear O2 is a simple 3-wire unit, two white, one black.

[99SUS SFD]

Yeah the mechanical spacer is on there.

I know it's not hard to do, but I snipped all 3 wires at once when I was splicing them and may have confused the white wires.

[decke48]

i think on 3 wire o2 whites are for the heater. as long as you hook them up to heater wires you cant screw it up since the polarity can go both ways. and the black is the signal.

[99SUS SFD]

Really? I wonder what the hell is going on then.

[decke48]

wasnt the CEL heater core low circuit bank 2? you might want to resolder your connections.

[99SUS SFD]

I'm getting codes P0133 and P0141, so yes that sounds right. After reading this, http://www.obd-codes.com/p0141, it sounds like I should put the new sensor in, but pay more attention to the wiring to make sure the right connections are being made.

[99SUS SFD]

So I bought some ramps today and just put my car up on them to take a look at what was going on. I noticed that the dumbass at the shop put the spacer on for the first sensor, before the cat, not after like where I told him to put it. So I'd imagine taking the spacer out and putting the sensor right in the pipe where it should be would correct the P0133 code? I need to get some wrenches that'll fit so I can take the sensor and spacer out. Then I'll work on the rear sensor.

[decke48]

lol. yes moving the spacer should take care of the p0133 code. make sure the wiring is good. if so the o2 may be at fault

[99SUS SFD]

That's what I get for having someone else perform work I'm capable of myself. :roll:

I'll just replace the sensor altogether, probably wouldn't hurt.

[Huffer]

So I bought some ramps today and just put my car up on them to take a look at what was going on. I noticed that the dumbass at the shop put the spacer on for the first sensor, before the cat, not after like where I told him to put it. So I'd imagine taking the spacer out and putting the sensor right in the pipe where it should be would correct the P0133 code? I need to get some wrenches that'll fit so I can take the sensor and spacer out. Then I'll work on the rear sensor.

OMG. Yes, spacer on the rear O2 will fix the problem I'm sure!

[99SUS SFD]

That would make my day. Nope, my month.

[99SUS SFD]

So I finally had a free day to crawl under my car and change the spacer around. Since I had brand new oxygen sensors, I replaced the front one when I took the spacer out. I'll replace the rear sensor when I make myself a nice set of extension wires versus the ghetto job that's on there now. Put the spacer on the rear and re-installed the sensor. Fired her up, tried to clear the CEL's, but they stayed on. Same codes as before. But I kept trying to reset the codes and on about the 4th try it finally took and they cleared. Hopefully they'll stay off, too. Pretty psyched though!

[T_F_E]

awesome

[99SUS SFD]

As my luck turns out, 2 minutes after I posted, my CEL came back on again with the P0141 code. So I bit the bullet and cut up my new O2 sensor and did a proper extension on the wires. All shrink wrapped and all. So far so good. 2 new oxygen sensors and she appears to be happy.

*Keeps fingers crossed*