Powertrain Controls - ECM/PCM

DTC 21 Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION:

The Throttle Position Sensor (TP) provides a voltage signal that changes relative to the throttle blade angle. Signal voltage will vary from about 0.2 to 0.95 volts at idle, to about 5.0 volts at Wide Open Throttle (WOT). The TP signal is one of the most important inputs used by the ECM for fuel control, and for most of the ECM controlled outputs.


TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. A DTC 21 will set under the following conditions:
^ TP signal voltage is greater than 2.5 volts
^ MAP reading below 52 kPa (7.5 psi) or greater than 15" Hg (vacuum).
^ All the above conditions are present for at least eight seconds.

2. With the TP sensor disconnected, the TP signal voltage should go low if the ECM and wiring are OK.

3. Probing circuit 452 with a test light to 12.0 volts checks the sensor ground circuit. A faulty ground will cause a DTC 21.


DIAGNOSTIC AIDS:

^ A "Scan" tool displays TP in volts. Closed throttle voltage should be between 0.2 to 0.95 volts, and the voltage value should increase at a steady rate as the throttle is opened with the ignition "ON" or engine idling.

^ A DTC 21 will result if circuit 452 is open. If a Code 21 is intermittent, - Intermittent Malfunctions