P0030 and P0134
 

Hi All,

Was told to post here to get some insight on what to do.

Background
April 2020
Brought car to a shop to install Gruppe-S UEL Headers
OFT Tuned for Stage 2+
Ran for a month no issues

Issue
After said month, felt loss of power, thought I just sucked at driving manual
CEL Popped after driving 1-2 hours
Scanned the code for P0030 And P0134.

Let it sit overnight, cleared the codes and it drove normally (no loss in power).
Drove for another hour, CEL popped again.

Attempted fix
Tried to reseat the O2 sensor (right side/gray connector)
Replaced O2 sensor (DENSO 2349136 {#22641AA640, 22641AA66A, SU00300425}).
Cleared the CEL and drove it for a week no issues (though trips were <1 hour)

Drove 1.5 hours, CEL popped.
Checked the fuse according to this thread.
Checked the EFI(HTR) and it was fine. No issues based on visual inspection.

Follow up #1
Near the end of the 1.5 hour trip mentioned above, a loud sound could be heard on deceleration and/or hitting regular road bumps (non potholes. Think line-fillers).

I initially thought it was it was my front lip falling off on one side and scraping the road. Stopped the car, checked it out, nothing was scraping. It sounded like sand paper against concrete, or a front lip scraping the road.

Follow up #2
Today I took off the underbody panel and saw this (i didnt install the header; took it to a shop).
https://i.imgur.com/oPsKKHm.jpg

Checked for exhaust leaks, didn't feel any air on hand. Checked O2S1 Voltage Deltas and got this:
https://i.imgur.com/4cpcaMF.png

The question now is this: Why does the O2S1 sensor report no activity seemingly after longer trips? Inconsistent Electrical connection due to heat?

Any insight is appreciated!

Thanks!

I feel like it's the resistance more than the voltage that is what is important with those. Like I'm pretty sure my old WRX we just replaced my 02 sensor with a 9 ohm resistor and it never complained again...

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Unfortunately I don't think that's a viable solution. It should be diagnosable and repairable without a band-aid solution.

Yeah I didn't think that was the route you wanted to go, lol. I was more making the point that it mighy be oHms not volts you should be worried about. I could be wrong though maybe volts is the right thing to test.

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Follow up #4

I left it be for a while and took it for a long drive today (40m-1h). Kept monitoring the 02 Sensor voltage to make sure it was updating. No issues. Will report back if the codes come back.

Follow up #5

So during the course of 1.5 weeks, I drove very little. Every trip resulted in a CEL with the exact same codes. Reflashed the ROM with no success.

Decided to spray the contacts with electrical cleaner and plugged it back in. Here is the real kicker: I tugged on it to see if it was snug - it was not. I tried to reseat, with no success. I grabbed pliers and pinched the connectors together and heard a click.

Drove around for another hour and a half - P0171 - High airflow/imbalanced AFR. Engine was definitely bogging and this is most likely the ECU retuning to live sensors finally reporting data. Let it cool down and tried again. Solid. Rock solid.

Attempted fix:
Make sure the connector is connected snug with the clip engaged. I believe the mech who installed the headers and therefore the O2 sensors didn't plug it in all the way and cleared the contacts causing intermittent issues. Every time would plug them in would reengage the contacts, but not securely resulting in the repeated codes.

Use angle grips to press the connectors together.
https://i.imgur.com/imP7q3t.png

So this came back to bite me about a week and a half later.

I refused to go to a mechanic and tried to resolve it myself.

I tried the following:

• Tracing the O2 sensor wires to the ECU plug
• Swapping the sensor
• Flashing 3 other tunes

None of this worked so I decided to revert to the stock header. I went to get gaskets before going under.

Here are the part numbers FYI:

Overpipe gasket 44011AG000
Manifold Gasket 44011AC030

Visually Inspecting I saw that there is some carbon build up where the gasket maker used to be.

https://i.imgur.com/PJcwAYX.png

I figured trying a simple gasket swap would work. Inspecting the gasket, it's clear the shop reused the overpipe gasket (which imo is a big nono).

It's clear that the gasket was reused and caused a small exhaust leak. This apparently is a known cause such codes to trip. Despite not having an audible indicator of an exhaust leak, the picture should be enough evidence.

https://i.imgur.com/NdVmCqR.png

It's been 2 weeks since the gasket replacement and no CELs. If I get them, I'll update this post with a solution.

That's all for now!

Thanks for giving us an update! Let us know if that fixed the codes permanently.

Isn't the new gasket smaller in diameter?

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It's been another 10 days since the update and no issues!

Stock overpipe diameter is ~2.1". The (new) gasket diameter matches that. The old one is 2.5" which still sits and seals fine, you just have an internal "gap".