Issues with 3rd O2 sensor on 2005 Wagon

[squidflakes]

Hello, 

I bought my kid a beat to hell 2005 Legacy Wagon but didn't notice until I had it in my driveway that it is the low emissions variant with the three cats and five O2 sensors. 

As we were starting it up to take it to get the state inspection done the MIL came on and it started throwing P0420 and P0143 for Bank 1 Sensor 3. 

On removing the old sensor I ran in to a couple of issues. The first was that the new cable wasn't nearly long enough to reach the connector. Second, the connector is the same six wire layout as the F/A sensors, but the replacement O2 sensor is a 4 wire. Third, I don't know if this is factory or someone at a shop making due, but about half way down there is some sort of 4 wire to 6 wire adapter which is crimped on to the old O2 sensor wires. 

Does any one know if there is an O2 sensor available with a long enough cable and the 6 pin pigtail? Is that P0143 code for low voltage because a wire is missing? 

 

I've attached some pictures for clarity. 

 

First is the 6 pin connector, with a scant 5 available pins. 

Second is the pigtail and the adapter on the other end of that wire. 

Third is the old O2 sensor and its side of the adapter. I can't imagine that kind of crimp job is from the factory.

 

 

 

[Infosecdad]

This looks like it in the Subaru Parts diagram: https://parts.subaru.com/a/Subaru_2005_Legacy-25L-4AT-WAGON/_54102_6024414/EXHAUST/B13-440-02.html

Looks like there is an extension cable in the mix as well, hard part is probably trying to find it, which might be why you are looking at what the previous owner did,

Did you get an OEM 02 sensor for your #3 replacement?

[KZJonny]

1 hour ago, Infosecdad said:

This looks like it in the Subaru Parts diagram: https://parts.subaru.com/a/Subaru_2005_Legacy-25L-4AT-WAGON/_54102_6024414/EXHAUST/B13-440-02.html

Looks like there is an extension cable in the mix as well, hard part is probably trying to find it, which might be why you are looking at what the previous owner did,

Did you get an OEM 02 sensor for your #3 replacement?

Oh geez... that parts diagram makes my head hurt. Soo many sensors. And where is the turbo? 

[squidflakes]

2 hours ago, Infosecdad said:

This looks like it in the Subaru Parts diagram: https://parts.subaru.com/a/Subaru_2005_Legacy-25L-4AT-WAGON/_54102_6024414/EXHAUST/B13-440-02.html

Looks like there is an extension cable in the mix as well, hard part is probably trying to find it, which might be why you are looking at what the previous owner did,

Did you get an OEM 02 sensor for your #3 replacement?

Thank you for linking that diagram, I really appreciate it!

The sensor I got is the Denso, so should be good there. 

[silverton]

Sorry I'm not much help here, other than I can say without a doubt that's not a factory connector/crimp job.  my shop has one of these as a loaner, i'll try to remember to get it in the air and take a look

[squidflakes]

8 hours ago, silverton said:

Sorry I'm not much help here, other than I can say without a doubt that's not a factory connector/crimp job.  my shop has one of these as a loaner, i'll try to remember to get it in the air and take a look

Hey Silverton, I'd really appreciate that. 

I did manage to find the wiring diagrams for the 2005 but they leave a little bit to be desired.

If I'm reading these right, it looks like the rear O2 sensor just uses 4 wires, with the two heater wires wrapped together and the signal and ground wires going to a bus or common connector with the other downstream O2 sensors. Putting that together with the parts list that KZJohnny provided it looks like there should be a mini harness and some breakout pigtails, but without that, the set-up I've got should work fine. 
 

[KZJonny]

Can’t take credit for the parts diagram. That was @Infosecdad.

I was just being sarcastic.

But glad that it’s working out for you. Kind of a crazy DIY on the 6/4 wire conversion, but great that it can work at least.

[squidflakes]

13 hours ago, KZJonny said:

Can’t take credit for the parts diagram. That was @Infosecdad.

I was just being sarcastic.

But glad that it’s working out for you. Kind of a crazy DIY on the 6/4 wire conversion, but great that it can work at least.

I should have the new sensor and the Frankenextender back in today so we'll see if it actually works. 

 

And d'oh! Yeah, thank you @Infosecdad for the part diagrams! 

Edited May 14 by squidflakes

[squidflakes]

Ok, fun update! 

I probably over did it matching up the sensor wires to the DIY harness work-around but the sensor went in, the car started, the CEL for the sensor went away and I went for a nice drive cycle to try and get this thing to pass emissions. 

 

Then the rear diff blew out on the freeway! 

 

[KZJonny]

1 hour ago, squidflakes said:

Ok, fun update! 

I probably over did it matching up the sensor wires to the DIY harness work-around but the sensor went in, the car started, the CEL for the sensor went away and I went for a nice drive cycle to try and get this thing to pass emissions. 

 

Then the rear diff blew out on the freeway! 

 

Oh jeeez.