The throttle actuator is used to control the amount of air and fuel mixture to the engine. A butterfly valve within the body is positioned by an electric actuator that is controlled by DDEC III/IV.
Listed in Table are the throttle control diagnostic codes:
| Description | Condition | PID | FMI | Information |
| Throttle Plate Position | HIGH Voltage | P51 | 3 | Indicates that the Throttle Plate Position Sensor input to the ECM has exceeded 95% (normally >4.75 volts) of the sensor supply voltage. This diagnostic is typically an open sensor return circuit or sensor signal circuit is shorted to the sensor +5 volt supply. |
| Throttle Plate Position | LOW Voltage | P51 | 4 | Indicates that the Throttle Plate Position Sensor input to the ECM has dropped below 5% (normally < 0.25 volts) of the sensor supply voltage. This diagnostic condition is typically detected when there is:- An open sensor signal circuit- An open sensor +5 volt supply circuit- The sensor signal is shorted to the sensor return circuit or to ground. |
| Throttle Plate Position | HIGH Position | P51 | 0 | Indicates that the Throttle Plate Position Sensor input to the ECM has indicated that the throttle plate has exceeded the recommended operating range. |
| Throttle Plate Position | LOWPosition | P51 | 1 | Indicates that the Throttle Plate Position Sensor input to the ECM has indicated that the throttle plate has dropped below the recommended operating range. |
