Minimum Function System

Fig. 003 - Chart - Code 21 Throttle Position Sensor Circuit (Open or Misadjusted).:

1. Checks the circuit from the TPS connector back to the ECM. Both wires should read about 5 volts.
2. Checks to see if the fault of low voltage at the TPS connector is an open in the circuit or a faulty ECM connector or ECM. A normal reading at the ECM is about 5 volts.
3. This step simulates closed throttle so, dwell should increase if the ECM is good.
4. This step tests the resistance of the TPS switch itself. A normal reading is under 20,000 ohms.