Upgraded Emissions

Disconnect negative battery cable. Remove air cleaner. Disconnect electrical connector from TP sensor. Loosen TP sensor retaining screws. Check if Idle Speed Control (ISC) motor plunger is contacting throttle lever screw.
If ISC motor plunger is contacting throttle lever screw, bring engine to normal operating temperature. Connect scan tester to DLC and turn ignition on. Insert a .14" (3.5 mm) feeler gauge between throttle lever and stop screw. See Fig 1 . Observe voltage on scan tester.
If TP sensor voltage is not .98-1.02 volts, rotate TP sensor until voltage is as specified. Remove feeler gauge. Reconnect electrical connector and install air cleaner.

Fig 1: Adjusting TP Sensor (Typical)

Courtesy of GENERAL MOTORS CORP.

Fig 2: TP Sensor Terminal ID (Standard Emissions)

Courtesy of GENERAL MOTORS CORP.