DTC 22

Code 22 "Throttle Position Sensor (TPS) Circuit":

Wiring Diagram - Throttle Position Sensor:

CODE 22

THROTTLE POSITION SENSOR (TPS) CIRCUIT (SIGNAL VOLTAGE LOW)


Circuit Description:
The Throttle Position Sensor (TPS) provides a voltage signal that changes, relative to the throttle blade. Signal voltage will vary from about .4 at idle, to about 4.9 volts at wide open throttle. 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.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 22 will set if the engine is running and the TPS signal voltage is is less than about .2 volt for more than 20 seconds.

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

Diagnostic Aids:

A "Scan" tool displays TPS input voltage as an indication of throttle position. TPS voltage should be .31 to .41 volt with throttle closed, ILC retracted and ignition "ON." TPS voltage is normally between .475 and .625 volt with engine at warm idle. However, the ECM "normalizes" or "learns" the idle TPS voltage, so that an idle TPS voltage between .2 volt and .7 volt is acceptable and need not be corrected. TPS voltage should increase at a steady rate as the throttle is opened and should reach at least 4.5 volts at wide open throttle.


Also, some "Scan" tools will display throttle position as an angle. About 10% = closed throttle, 100% = WOT. An open in CKT 416 or a short to ground in CKTs 416 or 417 will result in a Code 22. Check For:

Poor Connection OR Damaged Harness - Inspect ECM harness connector for backed out terminal "21", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.

Intermittent Test If - connections and harness check out OK, monitor TPS voltage display, while moving related connectors and wiring harness. If the failure is induced, the TPS display will abruptly change. This will help to isolate the location of the malfunction.

TPS Scaling - Observe TPS voltage display, while depressing accelerator pedal, with engine stopped and ignition "ON." Display should vary from closed throttle TPS voltage specification, when throttle was closed, to over 4.5 volts when throttle is held at wide open throttle position.