I have a 1997 z28 this code poped up its p0118 says engine coolant temp circuit high input. I replaced the coolant temp sensor and the air temp sensor. please help me out!

 

The PCM is seeing abnormally high voltage from the sensor. Did you replace the sensor in the water pump (not the one in the block). Check out the connection pigtail and wiggle the wires ..

 

I replaced the one in the water pump and have wiggled the wires, my friend says it could be the alternater what do You think?

 

I really doubt it, but you can verify pretty quick with a DVM or your dash gauge. W/engine running and lites, ect off you should have about 13.5 volts at the battery , put on headlights and you should maintain above 12 volts volts at the battery, usually is closer to 12.7-13.2 V and never below 12. Back to the sensor ...Shoebox has a super write up on testing the sensor and the harness, it requires a meter. " http://shbox.com/1/4th_gen_tech2.html#ect " Since you replaced the sensor already make sure the +5v from the PCM is good and the and the PCM ground reference side is OK...