ECM Code EO21, Shorted TPS Circuit: Action:

ECM turns on SERVICE ENGINE SOON light and disables viscous converter clutch. ECM uses 6 degrees for TPS value when ISC throttle switch closes. ECM uses 13 degrees for TPS value when ISC throttle switch opens.

The TPS is a 3-wire sensor receiving a 5-volt reference input from ECM over circuit No. 474, and a reference ground from ECM over circuit No. 976. The TPS sends a sensor output signal over circuit No. 417 to the ECM. The sensor output signal is a D voltage varying with throttle angle, TPS signal voltage is low (about .5 volt at minimum air setting). At high throttle angles, the TPS signal voltage is high (about 4.5 volts at wide open throttle). Code EO21 sets when ECM sees a high throttle angle (high TPS voltage) at low engine RPM. Code is designed to detect a TPS signal, over circuit No. 417, shorted to voltage.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Test Number 1) This step helps locate short to voltage. Short will be in TPS or circuit No. 417.

Test Number 2) This checks for an open ground in circuit No. 976. An open ground circuit will result in high TPS values whenever the TPS is plugged in.