6–30 Copyright © 1998 General Motors Corp.
WTEC II ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
7. If the condition persists, replace the ECU. If replacing the ECU corrects the problem, reinstall the
original (bad) ECU to confirm that the problem is in the ECU. If the original ECU now works,
inspect the ECU connectors for any corrosion or damage which may cause an intermittent
condition. If the original problem reoccurs, reinstall the replacement ECU.
8. The only troubleshooting necessary for a PWM fault is to check for an open, short-to-ground, or
short-to-battery in the signal wire from the PWM source. An open or short-to-ground will set
Code 21 12. A short to battery will set Code 21 23.
NOTE: A good throttle position sensor should have resistance of:
1. 9000–15,000 Ohms across terminals A and C.
2. 500 ohms, moving to 9000–15,000 Ohms as TPS is stroked (measured across terminals A and B).
CODE 21 XX — THROTTLE POSITION SENSOR OR PWM FAULT OR
ADJUSTMENT (Figures 6–5, 6–6)
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