Powertrain Controls - ECM/PCM

Code 22 Chart:

Throttle Position Sensor (TPS) Wiring Diagram:

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 at idle to about 4.8 volts at Wide Open Throttle (WOT). 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.

NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.


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

1. Code 22, will set if:

- Engine running.
- TPS signal voltage is less than about 0.2 volt.

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 reading is within the range of 0.29 to 0.98 volts, the ECM will use that value as closed throttle. If the existing or new TPS sensor is out of voltage range, make sure the cruise and throttle cables are not being held open. If ok replace TPS.

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

5. CKTs 416 and 474 share a common sensor ground 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 22 problem, disconnect it to see if Code 22 resets. Be sure 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 WOT. Also some "Scan" tools will read throttle angle 0% = closed throttle 100% = WOT An open or short to ground in CKTs 416 or 417 will result in a Code 22. Also, a short to ground in CKT 474 will result in a Code 22. Refer to TESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS.