Diagnostic Aids

With throttle closed, TPS voltage should be less than .80 volt. TPS voltage should steadily increase as throttle is opened. Code 21 will result if circuit No. 452 is open or circuit No. 417 is shorted to voltage. If code is intermittent, see TESTS W/O CODES article.

Fig 1: Code 21, Circuit Wiring Diagram

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code 21, Flow Chart

Courtesy of GENERAL MOTORS CORP.