My Corvette have rough idle, a member advice me to check the TPS.  Put in a new 1 from Advanceauto, same problem code 22

Ordering a new TPS AC/Delco brand, while waiting I tested the TPS with a voltmeter.  I am getting 6.28 vdc from the power source, and .28 vdc from the signal line.  Is it normal to get 6.28 vdc?  Or do I have another problem elsewhere? 

.28 vdc does not change when adjusting the TPS and voltage does not change when I move the spring switch.

All advice is appreciated.  Thanks.

TPS harness connector should have a black, a grey, and a dark blue wire. With the TPS disconnected, you should see a 5volt reference on the GREY wire with the key on. The black wire is the 5v reference RETURN(ground) signal to the ECM(this circuit also connects to the coolant temp sensor, and the Ecell timer circuits). The dark blue wire is the TPS voltage signal to the ECM. You should see around .50v at idle, and it should sweep evenly up to at least 4v at wide open throttle with the TPS connected, key on.

A problem with the coolant temp sensor, ecell timer, or a compromised splice/connection on the black wire could cause your TPS signal to the ECM to be erroneous, assuming you have 5v(approx) on the grey wire. Check the TPS voltage by back-probing with your multimeter to the black, and dark blue wires, key on, engine off.

Joel Adams
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Thanks for the advice.  I received my TPS and installed it.  Adjusted to .52 vdc and check voltage while pulling on the lever.  

Voltage moves up to 5+ vdc.  Started engine, RPM fluctuate from 500 rpm to 1900 rpm slowly move back down to 500 RPM and back up  etc.

Should I replace the coolant sensor?  Any other advice?  Thanks.