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Oxygen sensor codes indicating other issues upstream

Tiny
1ERALBRIGHT
  • MEMBER
  • 2008 HONDA FIT
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 195,000 MILES
My car has posted the codes:

P0138, B1S2 O2 sensor high voltage
P0139, B1S2 O2 sensor slow response
P0420, catalytic convert inefficiency
P2646, rocker arm actuator

To address the codes related to the oxygen sensor I first replaced it with a new sensor spliced into the old wires. When that didn't resolve the codes I replaced it with a direct fit OEM sensor. Still coding. I doubt that the sensors are defective, and the wiring harness appears in good shape since it is in the interior of the car and the slow response code suggests an existing connection. Could there be an issue upstream of the sensor that could be the cause? Vacuum leak? Bad computer? Where should I look? The car runs well enough in spite of the code, albeit with smelly exhaust and less mileage.
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Thursday, June 6th, 2019 AT 8:19 PM

8 Replies

Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

DTC P0139 and DTC P0420 are probably going to be a direct result of DTC P0138. I have included in the diagrams down below the explanation of DTC P0138, although I would double check the spliced wires from earlier to make sure they are spliced correctly. I have also included a connector pinout for your vehicle's secondary O2 sensor with the wire highlighted that you need to check. If that turns out okay, you will need to check for a short to power on this wire. To do this follow the wire and look for where it will touching a hot wire from another circuit, shorting out and getting power from the other circuit. Finally I have included factory diagnostic troubleshooting instructions for DTC P2646 although they do require the use of Honda's factory code reader called a HDS. Please go through these guides and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros
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Thursday, June 6th, 2019 AT 10:55 PM
Tiny
1ERALBRIGHT
  • MEMBER
  • 16 POSTS
Will do and thanks for the guides. I would like to add that my wife thinks she is hearing a louder, grumbling noise from the engine or as if a pot was boiling with a lid.
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Friday, June 7th, 2019 AT 4:02 AM
Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

This sounds like it could be a problem with your cooling system. Is your vehicle running hot at all?

Thanks,
Alex
2CarPros
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Friday, June 7th, 2019 AT 9:17 AM
Tiny
1ERALBRIGHT
  • MEMBER
  • 16 POSTS
The high temperature indicator on the dash has not come on. Coolant levels are okay. I have to wonder if a leaky intake manifold gasket would cause this noise and mess with the fuel air ratio downstream.
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Friday, June 7th, 2019 AT 12:06 PM
Tiny
1ERALBRIGHT
  • MEMBER
  • 16 POSTS
This afternoon I pulled out the console and checked the wiring from the connector to the ECM. Close after the connector the wires are wrapped and taped into their sleeve going into a triple harness that joins as it runs up behind the dashboard and through the firewall, and into the ECM next to the engine. It all looks clean, undamaged and not tampered with as left by the factory. There haven't been any electronic modifications or additions to the car that would interfere (aftermarket radio, speakers, lights, etc.). So it seems unlikely that electrical interference or shorts are the culprit.
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Friday, June 7th, 2019 AT 1:50 PM
Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello again,

When I was referring to the cooling system, it was in response to the "tea kettle" noise your wife was describing. I have a couple of links, though, for you to go to down below.

https://www.2carpros.com/articles/engine-noises
https://www.2carpros.com/articles/car-whistling-noise

Please go through these guides and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros
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Friday, June 7th, 2019 AT 9:39 PM
Tiny
1ERALBRIGHT
  • MEMBER
  • 16 POSTS
Hi again. The O2 sensor issue hasn't yet been resolved but I did locate the source of the noise in the engine. It was the sound of the A/C compressor clutch grinding and locking. Apparently it was choked with dirt and the bearings finally gave way. Removed the compressor and the wheel was loose in its track and not smooth. Replaced the compressor with a grade B used one, but that one came without a connector for the three red/hot wires. Am I right to assume that these equally thick wires are not interchangeable using the male connector from the old compressor?
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Monday, June 24th, 2019 AT 1:04 PM
Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello again,

I am not sure what kind of AC compressor you purchased but the connector should work on it. I have included the connector pinout for your vehicle's original AC compressor as well as a wiring diagram so you can see where the wires from connector go to. Please go through this information and get back to us with what you are able to find out.

Thanks,
Alex
2Carpros
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Tuesday, June 25th, 2019 AT 1:33 AM

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