Q: Q: my check engine light came on.

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the people at autozone said that the o2 sensor is getting high voltage. what needs to be fixed?

My car has 135000 miles.
My car has an automatic transmission.

Hi - the "high voltage" remark from your parts house person means that the O2 sensor is seeing a steady "rich" mixture coming out of the engine, and responds by generating a 1 volt signal (vs 0 volts for a lean mixture). This could be caused by a coolant sensor that is reporting a colder coolant temperature to engine management than really exists, causing the engine to run too rich. Were there any other problem codes? The O2 sensor problem code is a symptom, not the cause. I would recommend having a Check Engine Light is On completed by a mobile, professional mechanic, such as one from YourMechanic, to diagnose this problem, get an accurate assessment of damage and cost estimate for repairs.

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