Page 6E2-48 DOHC Code 21A - TPS Circuit

Fig. 6E2-32:

6E2-48 DRIVEABILITY AND EMISSIONS (DOHC)

CODE 21A

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 valve. Signal voltage will vary from less than 0.9 volts at idle to about 4.5 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 many of the ECM controlled outputs.

Test Description:

Numbers below refer to circled numbers on the diagnostic chart.

(1) This step checks to see if Code 21A is the result of a hard failure or an intermittent condition.
A Code 21A will set if:
^ TPS reading above 2.5 volts.
^ Engine speed less than 1750 rpm.
^ MAP reading below 50kPa.
^ All of the above conditions present for 2 seconds.

(2) This step simulates conditions for a Code 21B. If the ECM recognizes the change, the ECM and CKT's
416 and 417 are OK.

(3) This step isolates a faulty sensor, ECM, or an open CKT 452. If the CKT 452 is open, there may also
be a Code 23A.

Diagnostic Aids:

A "Scan" tool displays throttle position in volts. Closed throttle voltage should be less than 1.25 volts. TPS voltage should increase at a steady rate as throttle is moved to WOT. A Code 21A will result if CKT 452 is open or CKT 417 is shorted to voltage. If Code 21A is intermittent, refer to Section "B".