Powertrain Controls - ECM/PCM

Code 21 Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION:

The Throttle Position Sensor (TPS) provides a voltage signal that changes relative to the throttle blade. Signal voltage will vary from about 0.6 at idle to about 5 volts at Wide Open Throttle (WOT). The TPS signal is one of the most important inputs used by the ECM for fuel control and for most of the ECM control outputs.


NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.

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

1. Code 22 will set if:

^ TPS signal voltage is greater than 2.5 volts
^ Engine is running
^ All conditions met for 3 seconds.
OR
^ TPS signal voltage over 4.8 volts with ignition "ON".
^ With throttle closed the TPS should read between 0.3 and 0.9 volt. If it doesn't check for proper adjustment or for bent linkage.

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

3. Probing CKT 452 with a test light connected to 12 volts checks the ground CKT, because a faulty sensor ground will cause a Code 21.

DIAGNOSTIC AIDS:

A "Scan" tool reads throttle position in volts. Should read between 0.3 and 0.9 volts with throttle closed and ignition on or at idle. Voltage should increase at a steady rate as throttle is moved toward WOT. If code 15 or 52 is also set, check CKT 452 for faulty wiring or connections. Refer to TESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS.