Copyright © 1998 General Motors Corp. F–3
WTEC II ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
APPENDIX F — THROTTLE POSITION SENSOR ADJUSTMENT
B. Throttle Position Sensor (TPS) Adjustment
When properly installed by the equipment manufacturer, the TPS should not require adjustment.
Confirm that the throttle sensor is installed to manufacturer specifications before adjusting the
throttle position sensor. The idle count should be 50 or higher and full throttle count 200 or lower.
The TPS is self-calibrating meaning there is no optimum closed throttle or wide open throttle count
value. As long as the counts are within the 50 to 200 range, the TPS is set properly. Total stroke of
85–130 counts must be maintained. Watch the movement of the throttle sensor as the controls move it
through its full stroke. Be sure there is no misalignment or obstruction to smooth movement through
the full stroke. Make certain the idle and full throttle positions are not in the error zones (refer to
Figure F–2). The error zones occur when the idle position is less than 14 counts, or when the full
throttle position is more than 233 counts. When idle or wide open throttle positions are in the error
zones, Codes 21 12 and 21 23 occur, respectively. These codes cause the transmission to shift as if the
throttle is fully depressed (100 percent throttle) affecting shift quality and causing decreased fuel
efficiency. Code 21 XX may be caused by a short or open circuit in the chassis harness or by incorrect
voltages. If this occurs, refer to Code 21 XX chart.
NOTE: Use Test Harness J 41339 for measuring voltages.
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