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Q: Speed sensor keeps going bad and Check Engine Light is on.

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What makes this car speed sensor keep going bad I have changed it 4times car does great until check engine light comes on then it stays in 2nd or 3rd gear

My car has 170000 miles.
My car has an automatic transmission.

A: This may potentially be related to a faulty...

This may potentially be related to a faulty transmission control module. As you may know, every time a gear change is required, the car's computer activates a transmission solenoid, which directs transmission fluid into the valve body to engage the correct gear. When this is faulty or not working properly, this can cause a delay in gear shifting or, in some cases, cause the car to not shift at all.

The speed sensors help to monitor the speed of the output shaft in the transmission which then relay this information to the transmission control module. It may be possible that the sensors are now working correctly, but the module is essentially making the signal of the sensor useless. I would recommend having an expert mechanic, such as one from YourMechanic, come to your location to determine why the Check Engine Light is on with the speed sensor and replace the sensor as needed.

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