All standard GM Throttle Position Sensors have 3 wires going to them. Typical wire colors are Grey, Black, and Blue.
The grey wire is the 5 volt reference supply from the PCM and this wire should have 5 volts on it at all times when the key is on.
The black wire is the ground supply from the PCM and this wire should be grounded at all times.
The blue wire is the signal wire from the TPS to the PCM. The voltage on this wire varies from about 0.50 volts or so at closed throttle to about 4 volts or so at wide open throttle.
If you are careful, you can push a needle or pin into the back of the TPS plug (while it is still plugged into the sensor) between the wire and the silicone seal and push it in far enough that it makes contact with the wiring terminal inside - this will allow you to test the voltage on these circuits while the TPS is still plugged in. Take care not to pierce the insulation on the wire or tear the silicone seal because if water gets into this connector, it can corrode the connections causing a failure.
I bet you are going to find either your TPS is not getting 5 volts on the grey wire or the sensor itself is bad and there is no voltage output on the blue wire - either of which condition can set the TPS code you are getting.
OVERKILL IS UNDERRATED
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