With Speed Density Update

Chart - Code 22 Throttle Position Sensor (Signal Voltage Low):

Throttle Position Sensor (TPS) Circuit:

CIRCUIT DESCRIPTION
The throttle position sensor (TPS) provides a voltage signal that changes relative to the throttle blade. Signal voltage will vary from about 0.29 volts at idle to about 4.8 volts at wide open throttle. The TPS signal is one of the most important inputs used by the Electronic Control Module (ECM) for fuel control and for most of the ECM control outputs.

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

1. Code 22 will set if:
^ The engine is running.
^ The TPS signal voltage is less than about 0.25 volt for 3 seconds.
2. Simulates Code 21: (High Voltage) If the ECM recognizes the high signal voltage, the ECM and wiring are OK.
3. TPS check: The TPS has an auto zeroing feature. If the voltage reading is within the range of 0.29 to 0.98 volts, the ECM will use that value as closed throttle. If the voltage reading is out of the auto zero range on an existing or replacement TPS; check for cruise control and throttle cables being held open. Check the TPS adjustment.
4. This simulates a high signal voltage to check for an open in circuit 417.
5. Circuits 416 and 432 share a common 5 volt buffered reference signal. If either of these circuits is shorted to ground, Code 22 will set. To determine if the Manifold Absolute Pressure (MAP) sensor is causing the code 22 problem disconnect it to see if Code 22 resets. Be sure the TPS is connected and clear codes before testing.

DIAGNOSTIC AIDS
A "SCAN" tool reads throttle position in volts. Voltage should increase at a steady rate as throttle is moved toward wide open throttle. Also some "SCAN" tools will read throttle angle 0% = closed throttle 100% = wide open throttle. An open or short to ground in circuits 416 or 417 will result in a Code 22. Also, a short to ground in circuit 474 will result in a Code 22.
Refer to Diagnosis by Symptom / Intermittents. - Intermittent Malfunctions