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Home >> Mitsubishi >> 2002 >> Eclipse GS, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self Diagnostics - 2.4L >> Diagnostic Tests >> DTC P0121: Throttle Position Sensor Circuit Range/Performance Problem >> Diagnostic Procedure
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Diagnostic Procedure

CAUTION: To prevent damage to Scan Tool (MB991502), always turn off the ignition before connecting or disconnecting the scan tool.
  1. Connect Scan Tool (MB991502) to the data link connector. Turn the ignition on. Set the scan tool to data reading mode for item 14, Throttle Position Sensor. With the throttle valve in the idle position, voltage should be between 0.335-0.935 volt. With the throttle valve in the full-open position, voltage should be between 4.39-5.29 volts. Turn the ignition off. If the sensor is operating properly, it can be assumed that this malfunction is intermittent, refer to INTERMITTENT DIAGNOSTIC TROUBLE CODES . If the sensor is malfunctioning, go to next step.
  2. Check connector B-07 at throttle position sensor for damage. See Figure. If the connector is in good condition, go to next step. If the connector is damaged, repair or replace it and go to step  14.
  3. Disconnect the connector B-07. Measure the resistance between throttle position sensor side connector terminal 1 and 4. Measure resistance between the throttle position sensor side connector terminal 1 and 3. Move the throttle valve from the idle position to the full-open position. Resistance should change smoothly in proportion to the opening angle of the throttle valve. If the resistance is normal, go to next step. If the resistance is off, replace the throttle position sensor and go to step  14.
  4. Disconnect the connector B-07 and measure at the harness side. Turn the ignition on. Measure the voltage between terminal 4 and ground. Voltage should be between 4.8-5.2 volts. Turn the ignition off. If the voltage is normal, go to step  7, otherwise go to next step.
  5. Check connector C-60 at ECM (M/T) or connector C-54 at PCM (A/T) for damage. See Figure or Figure . If the connector is in good condition, go to next step. If the connector is damaged, repair or replace it and go to step  14.
  6. Check for harness damage between throttle position sensor connector B-07, terminal 3 and ECM connector C-60, terminal 81 (M/T) or PCM connector C-54, terminal 46 (A/T). See Figure, Figure or Figure . If the harness wire is in good condition, replace the ECM or PCM and go to step  14. If the harness wire is damaged, repair it and go to step  14.
  7. Check the continuity at throttle position sensor harness side connector B-07. Disconnect the connector B-07 and measure at the harness side. Measure the continuity between terminal 1 and ground. The resistance should be less than 2 ohm. If the continuity is normal, go to step  10, otherwise go to next step.
  8. Check connector C-60 at ECM (M/T) or connector C-54 at PCM (A/T) for damage. See Figure or Figure . If the connector is in good condition, go to next step. If the connector is damaged, repair or replace it and go to step  14.
  9. Check for open circuit and harness damage between throttle position sensor connector B-07, terminal 2 and ECM connector C-60, terminal 92 (M/T) or PCM connector C-54, terminal 57 (A/T). See Figure, Figure or Figure . If the harness wire is in good condition, replace the ECM or PCM and go to step  14. If the harness wire is damaged, repair it and go to step  14.
  10. Check connector C-60 at ECM (M/T) or connector C-54, C-57 at PCM (A/T) for damage. See Figure or Figure . If the connector is in good condition, go to next step. If the connector is damaged, repair or replace it and go to step  14.
  11. Check for harness damage between throttle position sensor connector B-07, terminal 1 and ECM connector C-60, terminal 84 (M/T) or PCM connector C-57, terminal 78 (A/T). See Figure, Figure or Figure . If the harness wire is in good condition, go to next step. If the harness wire is damaged, repair it and go to step  14.
  12. Check the maladjusted throttle position sensor. If the output voltage is normal, go to next step. If the output voltage is off, adjust the it and go to step  14.
  13. Connect scan tool to the data link connector. Turn the ignition on. Set the scan tool to data reading mode for item 14, Throttle Position Sensor. With the throttle valve in the idle position, voltage should be between 0.335-0.935 volt. With the throttle valve in the full-open position, voltage should be between 4.39-5.29 volts. Turn the ignition off. If the sensor is operating properly, it can be assumed that this malfunction is intermittent, refer to INTERMITTENT DIAGNOSTIC TROUBLE CODES . If the sensor is malfunctioning, replace the ECM or PCM and go to next step.
  14. Carry out a test drive with the drive cycle pattern (OBD-II). Check the diagnostic trouble codes. If DTC P0121 is output, retry the troubleshooting. If the DTC is absent, the inspection is complete.
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