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Home >> Isuzu >> 1990 >> Impulse Automatic >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 1.6L >> Diagnostic Circuit Check >> Code 21A: TPS Circuit (Signal Volt High) >> Notes
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Code 21A: TPS Circuit (Signal Volt High): Notes

Throttle Position Sensor (TPS) provides a voltage signal which changes relative to throttle opening. Signal voltage varies from less than .9 volt at idle to approximately 4.5 volts at wide open throttle. The TPS signal is used by ECM for fuel control and most ECM controlled outputs.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. This determines if Code 21A is from a hard failure or an intermittent condition. Code 21A will set if TPS reading is greater than 2.5 volts, engine speed is less than 1800 RPM, vacuum reading at MAP is less 9 in. Hg., or if all conditions are present for 2 seconds.
  2. This step simulates conditions for a Code 21B. If ECM recognizes the change, the ECM and circuits No. 416 and 417 are okay.
  3. This step isolates a faulty sensor, ECM or an open in circuit No. 452. If open is present in circuit No. 452, Code 23A may also be present.
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