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Q: Shifting gears and speed

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My car has the check engine light on and the codes that popped up was the O2 sensor and no signal to the circuit two. But when I went to the mechanic they said that I need it and put it out but sensor but won't that affect my speeding limit? Because when I accelerate, it won't let me go over 30 mph

My car has 108000 miles.
My car's transmission is unknown to me.

A: Hi, thanks for writing in. When a car won’t...

Hi, thanks for writing in. When a car won’t go above a specified low speed, this means your car is in what is known as limp mode. For some reason the PCM (powertrain control module) believes it needs to protect the motor from further damage. Long story short, your car needs further diagnosis. Most technicians will test drive the cars they do repairs on to confirm they fixed your car. It could be that the O2 did need to be replaced, but that isn’t all that is wrong with the car.

There is a large variety of failures that can put a car into limp mode. Without more details such as stored codes and scan tool data, I would just be guessing. To get a firm diagnosis, I recommend booking the following inspection: Check engine light is on inspection

Good luck!

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