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Q: The TPS error code P0123 appears only when the AC is on

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I had the throttle position sensor replaced on the truck along with the connections and cables, because I was getting an error code P0123. The code indicates the throttle position sensor circuit high voltage. The code was cleared. However, each time I turn the AC on, this happens again. There is a low charge in the AC system, but no error codes appear. The AC compressor is working properly. When I drive the car without AC on, there is nothing out of the ordinary. Why does this code appear with the AC on?

A: Hello. The low charge in the A/C system is ...

Hello. The low charge in the A/C system is going to cause the A/C compressor to work harder than it should. This will put a greater load on the engine and may cause your throttle position sensor to give a bad reading. Have a certified technician set the A/C system to the proper levels and see if the P0123 code continues. Having the throttle body cleaned may also help fix this problem. If you need help with this, a certified technician from YourMechanic can come to your car's location to diagnose the code more thoroughly in order to have this corrected.

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