W T E C I I I E L E C T R O N I C C O N T R O L S T R O U B L E S H O O T I N G M A N U A L
3. If the throttle counts do not change or are erratic, check the throttle sensor wiring for opens, shorts
between wires, or shorts-to-ground. Also check for correct TPS voltages using test wiring harness
J41339. If wiring problems are found, isolate and repair the fault.
4. If the wiring is satisfactory, replace the throttle position sensor and adjust its linkage so the counts
are not in the error zones.
5. If the throttle sensor and its linkage adjustment are correct and the wiring to the sensor is satisfac-
tory, the condition is intermittent. Replace the sensor and properly adjust the new sensor.
6. If the condition recurs, use a spare wire, if available, or provide a new wire (St. Clair P/N 200153
may be used for this purpose) for the throttle sensor circuit.
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, in-
spect the ECU connectors for any corrosion or damage which may cause an intermittent condition.
If the original problem recurs, reinstall the replacement ECU.
A good throttle position sensor should have resistance of:
(1) 900015,000 Ohms across terminals A and C.
(2) 500 Ohms, moving to 900015,000 Ohms as TPS is stroked (measured across
terminals A and B).
CODE 21 XX THROTTLE OR PWM FAULT (Figure 54)