Federal Emissions

Code 22 Diagnostic Chart:

Throttle Position Sensor (TPS) Circuit Diagram:

CIRCUIT DESCRIPTION
The Throttle Position (TP) sensor provides a voltage signal that changes relative to the throttle blade. Signal voltage will vary from about .5 at idle to about 4.8 volts at Wide Open Throttle (WOT).

The TP sensor signal is one of the most important inputs used by the ECM for fuel control and for many of the ECM control outputs.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. DTC 22 will set if:
^ Engine running.
^ TP sensor signal voltage is less than about .25 volt for 10 seconds.

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

3. TP sensor check: The TP sensor has an auto zeroing feature. If the voltage reading is within the range of 0.29 to 0.98 volt, 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 TP sensor; check cruise control and throttle cables for being held open.

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

5. CKT 416 and CKT 474 share a common 5 volts buffered reference signal. If either of these circuits is shorted to ground, DTC 22 will set. To determine if the MAP sensor is causing the DTC 22 problem, disconnect it to see if DTC 22 resets. Be sure TP sensor is connected and clear DTC(s) before testing.

DIAGNOSTIC AIDS:

^ A Tech 1 (or equivalent) scan tool reads throttle position in volts. Voltage should increase at a steady rate as throttle is moved toward WOT.

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

^ CKTs 416 and 417 are routed through a mini harness. CKT 416 is connected to terminal "D" at the gray connector, CKT 417 is connected to terminal "H" at the black connector.

^ Scan TP sensor while depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from about 500 mV (.5 volt) when throttle was closed, to about 4800 mV (4.8 volts) when throttle is held at Wide Open Throttle (WOT) position.

^ Also some scan tools will read throttle angle.
^ 0% = closed throttle.
^ 100% = open throttle.

^ If DTC 22 is set, check CKT 416 for faulty wiring or connections.