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P0420 and O2 sensor readings

Help, Advice, Owners' Discussion and DIY Tutorials on the third generation Volvo V70 wagon and XC70 crossover, and second generation S80. Are you an owner? Prospective owner? Get in here and join us! Start a new topic or comment on an existing thread.

2008-2016 V70
2008-2016 XC70
2007-2016 S80

volvostud
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Year and Model: 1968 220, 2003 S60
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volvostud

P0420 and O2 sensor readings

Post by volvostud » Wed Jan 08, 2020 1:55 pm

2010 XC70 T6 102k. I've been getting intermitant P0420 codes for years, going back to probably 70k miles. Always just cleared them and then a few months later they come back. Now they come back more often. Read my O2 sensor readings and get a consistent 1.0 on the upstream sensor and get a 0.14-.65 on the downstream (often holding in the .6-.63 range), and since clearing my code 40 miles ago, no code/CEL.

So how much of a difference should their be on the downstream? I've seen some reports for other cars but not Volvo.

Repair wise, I never thought that a Cat was low mileage replacement part but the local Volvo shop just said they go out at 100-120k and would be $2500 to replace. Nope.

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RickHaleParker
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Re: P0420 and O2 sensor readings

Post by RickHaleParker » Wed Jan 08, 2020 3:07 pm

volvostud wrote:
Wed Jan 08, 2020 1:55 pm
2010 XC70 T6 102k. I've been getting intermitant P0420 codes for years, going back to probably 70k miles.
Have you checked for Air leak in the exhaust system? Perhaps something that opens and closes making the leak intermittent.
Intermittent electrical on one of the O2 sensors?
----------------------------------------------------------------------------------------------

ECM-P042000 Catalyst System Efficiency Below Threshold (Bank 1). General Failure Information. No sub type information

Diagnostic trouble code (DTC) information ECM-P042000

Condition
Engine Control Module (ECM) checks the efficiency of catalytic converter (bank 1) by switching between rich and lean fuel/air mixture. When the change-over is made, the signal from the rear heated oxygen sensor (HO2S) is checked and the time taken for the probe to switch.

The diagnostic trouble code (DTC) is stored if the engine control module (ECM) registers that the rear heated oxygen sensor (HO2S) switches too quickly and is interpreted as poor catalytic converter efficiency.

The diagnostic trouble code (DTC) can be diagnosed with the engine at operating temperature, approximately 15 minutes after the engine has first been started if the vehicle is driven (normal road load) at 70-90 km/h for 30-40 seconds.

Substitute value
Nothing.

Possible source
Air leak in the exhaust system.
Damaged front heated oxygen sensor (bank 1).
Damaged front catalytic converter (bank 1).

Fault symptoms
Malfunction indicator lamp (MIL) lit.
Platform: P80 1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package, Plant: Uddevalla Sweden.

Platform: X40 (Nedcar) 2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000. Plant: Born Netherlands.

Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0,
Plant Torslanda Sweden.
----------------------------------------------------------------
1997 S90, B6304S, AW30-42, Bosch Motronic 4.4 - Sold

volvostud
Posts: 3
Joined: Mon Aug 23, 2010 3:12 pm
Year and Model: 1968 220, 2003 S60
Location: Austin TX
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volvostud

Re: P0420 and O2 sensor readings

Post by volvostud » Thu Jan 09, 2020 3:11 pm

I need to get it up on stands and roll under it to see what I can see/hear. The car otherwise drives flawlessly. I did just fill it up with 93 and I know there is some confirmation bias, but it feels like it idles smoother.

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RickHaleParker
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Re: P0420 and O2 sensor readings

Post by RickHaleParker » Thu Jan 09, 2020 4:42 pm

One can smoke test the exhaust system by injecting the smoke up the tail pipe.
Platform: P80 1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package, Plant: Uddevalla Sweden.

Platform: X40 (Nedcar) 2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000. Plant: Born Netherlands.

Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0,
Plant Torslanda Sweden.
----------------------------------------------------------------
1997 S90, B6304S, AW30-42, Bosch Motronic 4.4 - Sold

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