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Home >> Mitsubishi >> 2003 >> Eclipse GT, Standard >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - 3.0L >> 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 the ignition off before connecting or disconnecting it.
  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. When the throttle valve is in idle position, voltage should be between 0.535-0.735 volts. With the throttle valve in the full-open position, voltage should be between 4.5-5.5 volts. Turn the ignition off. If the sensor is operating properly, it can be assumed that this malfunction is intermittent, refer to INTERMITTENT FAILURES  . If the sensor is malfunctioning, go to the next step.
  2. Check connector B-07 at throttle position sensor for damage. If the connector is in good condition, go to the next step. If the connector is damaged, repair or replace it and proceed to step  14 .
  3. Check the throttle position sensor. Disconnect the connector B-07. Measure the resistance between throttle position sensor side connector terminals No. 1 and 4. Standard value: 3.5-6.5 k/ohms. Measure resistance between the throttle position sensor side connector terminals No. 1 and 3. Move the throttle valve from the idle position to the full-open position. Resistance should change smoothly in proportion tot he opening angle of the throttle valve. If the resistance is normal, go to the next step. If the resistance is abnormal, replace the throttle position sensor (refer to THROTTLE BODY in appropriate REMOVAL & INSTALLATION article) and proceed to step  14 .
  4. Check the sensor supply voltage at throttle position sensor harness side connector B-07. Disconnect the connector B-07 and measure at the harness side. Turn the ignition on. Measure the voltage between terminal No. 4 and ground. Voltage should be between 4.8-5.2 volts. Turn the ignition off. If the voltage is normal, proceed to step  7 , otherwise, go to the next step.
  5. Check connector C-58 at ECM (M/T) or connector C-55 at PCM (A/T) for damage. If the connector is in good condition, go to the next step. If the connector is damaged, repair or replace it and proceed to step  14 .
  6. Check for harness damage between throttle position sensor connector B-07 terminal No. 4 and ECM connector C-58 terminal No. 42 (M/T) or PCM connector C-55 terminal No. 46 (A/T). If the harness wire is in good condition, replace the ECM or PCM, otherwise, repair the harness wire. Proceed 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 No. 1 and ground. The resistance should be less than 2 ohm. If the continuity is normal, proceed to step  10 , otherwise, go to the next step.
  8. Check connector C-58 at ECM (M/T) or connector C-55 at PCM (A/T) for damage. If the connector is in good condition, go to the next step. If the connector is damaged, repair or replace it and proceed to step  14 .
  9. Check for open circuit and harness damage between throttle position sensor connector B-07 terminal No. 1 and ECM connector C-58 terminal No. 49 (M/T) or PCM connector C-55 terminal No. 57 (A/T). If the harness wire is in good condition, replace the ECM or PCM, otherwise, repair the damaged harness wire. Proceed to step  14 .
  10. Check connector C-58, C-62 at ECM (M/T) or connector C-55, C-59 at PCM (A/T) for damage. If the connector is in good condition, go to the next step. If the connector is damaged, repair or replace it and proceed to step  14 .
  11. Check for harness damage between throttle position sensor connector B-07 terminal No. 3 and ECM connector C-62 terminal No. 78 (M/T) or PCM connector C-59 terminal No. 78 (A/T). If the harness wire is in good condition, go to the next step, otherwise, repair it and proceed to step  14 .
  12. Check the maladjusted throttle position sensor. Refer to THROTTLE POSITION SENSOR ADJUSTMENT in appropriate ON-VEHICLE DIAGNOSTICS article. If the output voltage is normal, go to the next step, otherwise, adjust the output voltage and proceed to step  14 .
  13. 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 0.535-0.735 volts. With the throttle valve in the full-open position, voltage should be between 4.5-5.5 volts. Turn the ignition off. If the sensor is operating properly, it can be assumed that this malfunction is intermittent, refer to INTERMITTENT FAILURES  . If the sensor is malfunctioning, replace the ECM or PCM and go to the next step.
  14. Carry out a test drive with the drive cycle pattern (Other Monitor), refer to Figure . Check the diagnostic trouble codes. If DTC P0121 is output, retry the troubleshooting. If the DTC is absent, the inspection is complete.
Fig 1: Throttle Position Sensor (TPS) Circuit
G00239370Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
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