Powertrain Controls - ECM/PCM

Diagnostic Trouble Code 22:

Throttle Position Sensor Circuit:

CIRCUIT DESCRIPTION
The Throttle Position (TP) sensor provides a voltage signal that changes relative to the throttle blade position. TP sensor signal voltage will vary from about 0.5 at idle to about 5 volts at Wide Open Throttle (WOT).

The TP sensor signal is one of the most important inputs used by the Engine 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. Diagnostic Trouble Code (DTC) 22 will set if:

^ Engine is running.
^ TP sensor signal voltage is less than 0.2 volt.

The TP sensor has an auto zeroing feature. If the voltage reading is within the range of about 0.3 to 1.0 volts, the ECM will use that value as closed throttle. If the voltage reading is out of the auto zero range at closed throttle, check for a binding throttle cable or misadjusted TCS adjuster assembly or damaged linkage. If OK, continue with diagnosis.

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

3. This simulates a high signal voltage to check for an open in CKT 417. The scan tool will not read up to 12 volts, but what is important is that the ECM recognizes the signal on CKT 417.

4. Refer to Diagrams/Electrical for detailed circuit description before replacing any components. Diagrams

5. If the TP sensor or throttle body is replaced, the Electronic Brake and Traction Control Module (EBTCM) must "learn" the TP sensor idle position voltage with the new component(s) installed. This is necessary to ensure effective engine torque reduction during Traction Control System (TCS) adjuster assembly or damaged linkage.

THROTTLE POSITION SENSOR LEARN PROCEDURE
This procedure requires a T-1 (Tech 1 scanner) or T-100 (CAMS) unit, and is as follows using a Tech 1 scanner:

^ Ignition "OFF."
^ Connect Tech 1 scanner with Mass Storage/Chassis Cartridge.
^ Ignition "ON."
^ Follow menus to reach ABS/TCS features.
^ Select "F5: TP SENSR LRN."
^ Press the up arrow to begin learn procedure.
^ Wait for Tech 1 scanner to indicate "Complete."
^ Ignition "OFF."
^ Disconnect Tech 1 scanner.


DIAGNOSTIC AIDS
A scan tool displays throttle position in volts. With ignition "ON" or at idle, TP sensor signal voltage should display from about 0.3 to 1.0 volts with the throttle closed and increase at a steady rate as throttle is moved toward WOT.

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

Refer to Intermittents in Diagnosis By Symptom. Testing and Inspection