i have a 03 tahoe displaying codes p1518 p1516 p1518 p2135 p1515 p0120 things i have checked and or replaced throttle body was replaced not by me but it is hatachi brand acdelco throttle position sensor pedal,plugs & wires along with pcv and engine air filter.i had a code for knock sensors and while i was replacing the knock sensors did new intake gaskets and fuel injector rings along with cleaning the one ground on driver side back side of block and oil pressure sensor was replaced due to covered in oil.i got the alternator and the battery checked they were reading at correct voltage. replaced the pigtail to the throttle body with the butt connectors that are coder ones too along with eletrical tape around each wire. checked all grounds cleaned and nothing rewired that ground that was on the back side of block on passenger side to where the ground is on fire wall. i also checked the wires that go to the tac module on the firewal and at the pedal sensor. i am now at a loss.
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