Without Electronic Transmission

Throttle Position Sensor Circuit Code 22:

Throttle Position Sensor Circuit:

Circuit Description:
The Throttle Position Sensor (TPS) provides a voltage signal that changes relative to the throttle blade angle. Signal voltage will vary from about .5 volt at idle to about 4.0 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.
On nonadjustable TPS switches, each time voltage drops below 1.25 volts and stops, the ECM assumes this value is 0 throttle angle and measures percent throttle from this point on.

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

1. This step checks to see if Code 22 is the result of a hard failure or an intermittent condition. Code 22 will set if:

- Engine running.
- TPS signal voltage is less than about .2 volts for 2 seconds.


2. Simulates Code 21: (high voltage) - If the ECM recognizes the high signal voltage, the ECM and wiring are OK.

3. The ECM recognizes the voltage as over 4 volts, indicating the CKT 417 and the ECM are OK.

4. This simulates a high signal voltage to check for an open in CKT 417.

5. If CKT 416 is shorted to ground, there may also be a stored Code 34.


Diagnostic Aids:
A Tech 1 "Scan" tool reads throttle position in volts. Should read about .45 to .95 volt 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).

An open or short to ground in CKTs 416 or 417 will result in a code 22.

SE. Intermittents


"Scan" TPS while depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from below 1.25 volts (1250 mV) when throttle was closed, to over 4.5 volts (4500 mV) when throttle is held at Wide Open Throttle (WOT) position.