Throttle/Petal Position Sensor/Switch C Circuit Low Input


This code indicates that the PCM has detected a throttle pedal position sensor switch C circuit voltage reading that is abnormal.

Code Set Parameters

Voltage/resistance variations that exceed 10-percent of the manufacturer’s specified reference voltage (with the throttle in any given position as compared to engine RPMs) will cause a trouble pedal sensor code to be stored and a service engine soon lamp to be illuminated.


Possible symptoms can include black smoke at startup, poor acceleration, a no start condition, misfire at idle, start and stall, and service engine lamp illumination.

Common Causes

Possible causes of this code include a defective throttle pedal position sensor, loose, corroded, or damaged electrical connector, faulty circuit wiring, faulty or misadjusted TPS pedal position sensor, faulty throttle body, or a faulty PCM. PCM failures are rare.

Common Misdiagnosis

Often the TPS sensor is replaced in error when the electrical connector face has been contaminated with moisture.


  • This code is relevant only to throttle systems that utilize a “drive-by-wire” configuration
  • Drive by wire uses a sensor located on the accelerator pedal to supply input data to the PCM
  • The PCM then opens and closes the throttle plate using various actuators, solenoids, and motors
  • A throttle position sensor is also used on the throttle body to monitor actual throttle position. The PCM reads a variable voltage reading (usually between .5 to 5.0-volts) graduated as the throttle pedal is depressed to determine the degree which the throttle body has to be opened
  • The PCM then commands the throttle drive by wire system motors and actuators to open or close the throttle plate as required. A scanner or code reader, a digital volt ohmmeter, and access to a manufacturer’s wiring schematic will be necessary to successfully diagnose this code
  • Begin your diagnosis with a visual inspection of all wiring and connectors
  • Repair or replace damaged, disconnected, shorted, or corroded wiring, connectors, and components as necessary
  • Always retest the system after repairs are completed to ensure success. If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data
  • This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored
  • After the codes are cleared, operate the vehicle to see if the code returns
  • If the code fails to immediately return, you may have an intermittent condition
  • Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made. To test the TPS pedal sensor, measure the reference voltage reading at the connector face as you manually activate the accelerator pedal
  • Watch for sudden jumps in voltage or glitches as the voltage drops
  • Throttle body mounted TPS adjustment is also critical to proper operation (if equipped)
  • If the TPS sensor checks out, begin voltage testing at the TPS pedal position electrical connector and proceed towards the PCM. If the throttle pedal position sensor appears to be operating normally, disconnect the PCM connector and perform a circuit continuity and resistance test between the PCM and the throttle pedal position sensor
  • Compare your findings with manufacturer’s specifications and replace circuitry, connectors, or components as required. When attempting to diagnose and repair this type of system, if the throttle body actuators, sensors, and/or other components are defective, you will likely discover that they are not serviceable and therefore not sold separately