Code 21 - Throttle Position Sensor (TPS) Circuit (Signal Voltage High)

Circuit Description

The Throttle Position Sensor (TPS) provides a voltage signal that changes relative to the throttle blade. Signal voltage will vary from about 0.5 at idle to about 5 volts at wide open throttle.

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

Problem Description:

Code 21 will set if:

• Engine running less than 1600.

• TPS signal voltage is greater than 2.5 volts.

• All conditions met for 2 seconds.

• MAP less than 70 kPa.

With throttle closed the TPS should read less than 1.25 volts. If it doesn't replace TPS.

Diagnostic Aids:

A Scantool reads throttle position in volts. It 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 WOT.

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

"Scan" Diagnostics:

Throttle closed.

Does scantool display TPS over 2.5 volts?

NO YES