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Home >> Mitsubishi >> 2003 >> Lancer Evolution >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - 2.0L Turbo >> 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, always turn ignition switch to LOCK position before connecting or disconnecting scan tool.
  1. Using scan tool, check throttle position sensor. Connect scan tool to data link connector. Turn ignition on. Set scan tool to the data reading mode for data list item 14: THROTTLE POSITION SENSOR. With throttle valve in idle position, voltage should be 0.535-0.735 volt. With throttle valve in full-open position, voltage should be 4.4-5.3 volts. Turn ignition switch to LOCK position. If sensor is not operating properly, go to next step. If sensor is operating properly, malfunction is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - LANCER TURBO article.
  2. Check throttle position sensor harness connector for damage. If connector is in good condition, go to next step. If connector is not in good condition, repair or replace as necessary. After repairs, go to step  14 .
  3. Check throttle position sensor. Using a DVOM, measure resistance between throttle position sensor terminals No. 1 and 4. Standard value is 4-7 k/ohms. Measure resistance between the throttle position sensor terminals No. 2 and 4. Move throttle valve from idle position to full-open position. Resistance should change smoothly in proportion to the opening angle of throttle valve. If resistance is as specified, go to next step. If resistance is not as specified, replace throttle position sensor. go to step  14 .
  4. Disconnect throttle position sensor harness connector. Turn ignition on. Measure voltage between TP sensor harness connector terminal No. 1 and ground. Voltage should be 4.8-5.2 volts. Turn ignition switch to LOCK position. If voltage is not as specified, go to next step. If voltage is as specified, go to step  7 .
  5. Check ECM harness connector C-115 (M/T) or PCM harness connector C-118 (A/T) for damage. If connector is in good condition, go to next step. If the connector is not in good condition, repair or replace as necessary. After repairs, go to step  14 .
  6. Check for harness damage between throttle position sensor harness connector terminal No. 1 and ECM harness connector C-115 terminal No. 84 (M/T) or PCM harness connector C-118 terminal No. 46 (A/T). If wiring harness is in good condition, replace ECM or PCM. After replacing ECM or PCM, go to step  14 . If wiring harness is not in good condition, repair wiring harness. After repairs, go to step  14 .
  7. Check continuity at throttle position sensor harness connector. Measure continuity between throttle position sensor harness connector terminal No. 4 and ground. Resistance should be less than 2 ohms. If continuity is not as specified, go to next step. If continuity is as specified, go to step  10 .
  8. Check ECM harness connector C-115 (M/T) or PCM harness connector C-118 (A/T) for damage. If connector is in good condition, go to next step. If connector is not in good condition, repair or replace as necessary. After repairs, go to step  14 .
  9. Check for open circuit and harness damage between throttle position sensor harness connector terminal No. 4 and ECM harness connector C-115 terminal No. 92 (M/T) or PCM harness connector C-118 terminal No. 57 (A/T). If wiring harness is in good condition, replace ECM or PCM. After replacing ECM or PCM, go to step  14 . If wiring harness is not in good condition, repair wiring harness. After repairs, go to step  14 .
  10. Check ECM harness connector C-115 (M/T) or PCM harness connectors C-116 and C-118 (A/T) for damage. If connector(s) are in good condition, go to next step. If the connector(s) are not in good condition, repair or replace as necessary. After repairs, go to step  14 .
  11. Check for harness damage between throttle position sensor harness connector terminal No. 2 and ECM harness connector C-115 terminal No. 84 (M/T) or PCM harness connector C-116 terminal No. 78 (A/T). If wiring harness is in good condition, go to next step. If wiring harness is not in good condition, repair wiring harness. After repairs, go to step  14 .
  12. Check for misadjusted throttle position sensor. See THROTTLE POSITION SENSOR in ON-VEHICLE ADJUSTMENTS article. If output voltage is as specified, go to next step. If output voltage is not as specified, adjust it throttle position sensor. After adjusting sensor, go to step  14 .
  13. Using scan tool, check throttle position sensor. Connect scan tool to data link connector. Turn ignition on. Set scan tool to the data reading mode for data list item 14: THROTTLE POSITION SENSOR. With throttle valve in idle position, voltage should be 0.335-0.935 volt. With throttle valve in full-open position, voltage should be 4.4-5.3 volts. Turn ignition switch to LOCK position. If sensor is operating properly, malfunction is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - LANCER TURBO article. If sensor is not operating properly, replace ECM or PCM. After replacing ECM or PCM, go to next step.
  14. Test the OBD-II drive cycle. Carry out a test drive with the drive cycle pattern. See OTHER MONITOR  under VERIFYING REPAIRS. Check for DTCs. If DTC P0121 is output, repeat diagnosis. If DTC P0121 is not output, inspection is complete.
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