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Flashing check engine light, cylinder one misfire and O2 sensor codes

Tiny
EMILY AUSTIN
  • MEMBER
  • 2009 SCION XD
  • 1.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 250,000 MILES
I have drivability issues such as hesitation with acceleration that improves when letting off gas, very rough low idle, check engine light flashing only when RPMs get to about 3,000 RPMs and codes indicate o2 sensor upstream a/f ratio issue and break in circuit between o2 sensor and ECM from what I can tell (p2237) and a cylinder one misfire (p0301). I have tried several things and would like to talk to a mechanic who knows Scions to see what they think and if I am heading down the wrong path or not. Please message me and I will gladly provide all the details you need.
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Friday, June 3rd, 2022 AT 12:04 AM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,602 POSTS
Hello,

The first thing we should do is remove the spark plugs to see if they all look the same, if the number 1 cylinder looks different then we need to do a compression test. Don't worry about the oxygen sensor codes right now because that could be a side effect of the cylinder misfire. Here is a guide to help you remove the spark plugs:

https://www.2carpros.com/articles/how-to-change-spark-plugs

If the plugs don't show anything reinstall the plugs and send me a video of the engine cranking over so I can see if you have compression in all cylinders. Let us know what happens and please upload pictures or videos of the problem.
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Friday, June 3rd, 2022 AT 2:30 PM

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