Q: My check engine light came on. Took it to Autozone and they came up with this code PO156. What is that

asked by on May 03, 2017

The check engine light came on today. I took it to Autozone and they ran a test. It came up with code PO156. What is that.

My car has 110100 miles.
My car has an automatic transmission.

Hello, thank you for writing in. A P0156 troubleshooting code stands for an error with the oxygen sensor. There are multiple sensors, and this one is behind (further towards the rear) the catalytic converter. Several things may be happening. First, the oxygen sensor may have failed, and needs to be replaced. These sensors can also get dirty, and give bad readings because it becomes harder to send their signals through contamination. The oxygen sensors are also there to help track how well the catalytic converter is working. One of the worst cases would be that the catalytic converter is damaged or melted inside. Only further testing of the sensor and the catalytic converter will tell. For more help with this testing and repairing the issue, contact our service department to schedule an appointment.

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