DTC 21

DTC 21 - Throttle Position (TP) Sensor Circuit (Signal Voltage High):

Throttle Position (TP) Sensor Wiring Circuit:

Circuit Description:

The Throttle Position (TP) sensor provides a voltage signal that changes relative to the throttle blade. Signal voltage will vary from about .5 at idle to about 4.5 volts at Wide Open Throttle (WOT).

The TP sensor signal is one of the most important inputs used by the ECM for fuel control and for most of the ECM control outputs.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. DTC 21 will set if:
^ TP sensor signal voltage is greater than 3.1 volts.
^ All conditions meet for 2 seconds.
^ MAP is less than 52 kPa.
2. With the TP sensor disconnected, the TP sensor voltage should go low if the ECM and wiring are OK.
3. Probing CKT 452 with a test light to 12 volts checks the sensor ground circuit. A faulty sensor ground will cause a DTC 21.

Diagnostic Aids:

A Tech 1 scan tool reads throttle position in volts. Should read less than 1.25 volts with throttle closed and ignition "ON" or at idle. Voltage should increase at a steady rate as throttle is moved toward Wide Open Throttle (WOT). Tech 1 will also display throttle angle. Key "ON" engine "OFF" Tech 1 will display less than 100% at Wide Open Throttle (WOT).

An open in CKT 452 will result in a DTC 21.

- Intermittent Malfunctions