Code P0420

Tiny
BRIAN MAGERS
  • MEMBER
  • 2011 VOLVO XC70
  • 3.0L
  • 6 CYL
  • TURBO
  • 4WD
  • AUTOMATIC
  • 170,000 MILES
I'm hoping someone can offer some assistance. I've got the vehicle listed above t6. Literally just got it yesterday shipped from Connecticut to California.

Problem is, it failed emissions with a permanent dct p0420.

I have an iCarsoft i906 and was looking through all the car data and ran across the o2 sensors running an odd voltage. From what I've read, the front (upstream) sensor should be fluctuating from 0.1v to 0.9v, however it's sitting at a solid 1.0v and not fluctuating.

My question, does anyone know if that is a bad reading for the front o2 sensor?

Thank you.
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Friday, May 15th, 2020 AT 1:34 PM

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Tiny
KASEKENNY1
  • EXPERT
You are correct. This upstream sensor produces voltage from around 0.1 volts to 0.9 volts. However, it doesn't necessarily switch. You are thinking of the short term fuel trims. Those should switch between negative and positive around 0.

The sensor voltages should be a little more steady around where the fuel mixture is. Meaning lean exhaust will be lower and rich is higher up to 0.9 volts. So either your exhaust it very rich or your sensor is the issue. If it were me, I would swap the sensors side to side and see if that one still reads 1.0 volts. If it does then the sensor is faulty and that should solve your issue.

Let me know if you have questions. Thanks
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Friday, May 15th, 2020 AT 5:50 PM

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