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Codes P0300 and P0051?

Tiny
YUM MAH
  • MEMBER
  • 2007 HYUNDAI SANTA FE
  • 3.3L
  • V6
  • 4WD
  • AUTOMATIC
  • 175,000 MILES
Last week, the check engine began flashing with p0300 random misfire. Diagnosed it to be coils #2 and #4 so I replaced the 3 old coils on the Bank 2 side. The 3 coils on Bank 1 were replaced within the last year.
Since p0300 showed up, now I'm getting p0050 p0051 and p0151 codes.
After clearing p0300, it came back several times. I pulled over, turned the car off, turned it back on again and was able to drive without any issues. This repeated a few times. Right now, I have a solid p0050, p0051 and p0153 codes indicating the o2 Bank 2 Sensor 1, plus the occasional p0300 misfire on all 6 cylinders.
The B2S1 o2 sensor is fairly new. I replaced all 4 o2 sensors, and all 6 coil packs, plus new NGK plugs.
Is it possible that the B2S1 gone bad, or front CAT now needs to be replaced?
Car has 175,000 runs strong, no leaks, new air filter, oil change, clean MAF, new 6 coils, new spark plugs, new 4 o2 sensors, one new CAT Bank1 and one old Cat Bank2.
Any advice is greatly appreciated.
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Sunday, January 15th, 2023 AT 4:21 AM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

The codes are related to O2 sensor voltage variations. I don't feel this is the catalytic converter because the codes are related to sensors that are before the catalytic converter. Basically, they are changing between a rich and lean mixture more than three times in ten seconds.

So, I have a feeling it is a connection issue. What I need you to do is connect a live data scan tool and with the engine at idle, watch the voltages at each of the sensors. They should be in the area of 150mV. Pay attention if they are jumping around. Keep in mind, they should change but at idle they should be somewhat steady.

Next, tap the throttle. Each one should change voltage. Are there any that don't change?

One last thing to watch. There should be a variance between sensor 1 and sensor 2. If they are nearly the same, the converter may not be doing its job. But that still shouldn't cause the codes you are getting.

Let me know. If you do note a sensor that sticks out as an issue, go to that one and inspect the connector and wiring.

Here is a link you may find helpful:

https://www.2carpros.com/questions/2002-toyota-avalon-no-start/page/5#last

Let me know what you find.

Joe
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Sunday, January 15th, 2023 AT 7:08 PM
Tiny
YUM MAH
  • MEMBER
  • 29 POSTS
Hi Joe,

Thank you for your excellent advice! You were right!
I loaded Live data and watched the 4 sensors, plus the two CATs temperatures. The temperatures were consistent. Both O2 sensors in Bank one were also as they should be.
But Bank two pre sensor (B2S1) was way up over 1.5v most of the time. So, I took it out B1S1 O2 sensor (a cheap KAX from Amazon, never again!), Plugged in my old O2 sensor and tested.
All 4 O2 sensors are in perfect harmony! I cleared the codes and drove long enough and no more codes.
Again Joe, thank you for saving me a ton of money and the headache of replacing a good CAT!
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Tuesday, January 17th, 2023 AT 4:59 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Thank you for the update. I'm glad you found the issue. Things like this can be so frustrating. LOL

Regardless, please feel free to come back anytime in the future if you have questions. You are always welcome here.

Take good care of yourself,

Joe
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Tuesday, January 17th, 2023 AT 5:52 PM

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