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Home >> GMC >> 1999 >> Forward Control 4.3 W, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes - DTC P0704-P1272 >> DTC P1221 >> DTC P1221: TP Sensor No. 1 & 2 Performance (3.8L "F" Body) >> Circuit Description
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Circuit Description

The Throttle Position (TP) sensor is a potentiometer, mounted on throttle body/TAC assembly. TP sensor is actually 2 sensors within one housing. Two separate signal, ground and reference circuits are used in order to connect the TP assembly and Throttle Actuator Control (TAC) module.

TP sensor No. 1 signal voltage increases as throttle opens. The signal circuit for TP sensor is pulled up to reference voltage. DTC will set when TP sensors No. 1 and 2 disagree by greater than.17 volts for less than one second.