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Home >> Mitsubishi >> 2002 >> Montero XLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0121: Throttle Position (TP) Sensor Circuit Range/Performance Problem >> Test Procedure
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Test Procedure

  1. Turn ignition on. Using scan tool, check data list item No. 14 (throttle position sensor). Turn ignition on. With throttle valve in idle position, voltage should be 0.535-0.735 volt. With throttle valve in fully open position, voltage should be 4.5-5.5 volts. If voltages are as specified, problem is intermittent. See INTERMITTENT DIAGNOSTIC TROUBLE CODES . If voltages are not as specified, go to next step.
  2. Turn ignition off. Disconnect TP sensor 4-pin connector. See Figure. Check TP sensor connector for loose, damaged, or corroded terminals. If problem exists, repair or replace connector. Go to step  14. If problem does not exist, go to next step.
  3. Measure resistance between TP sensor terminals No. 1 and 4 (component side). Resistance should be 3.5-6.5 K ohms. Also, measure resistance between TP sensor terminals No. 1 and 3 (component side) while moving throttle valve from idle position to full throttle position. Resistance should change smoothly in proportion to the opening angle of throttle valve. If both resistance checks are as specified, go to next step. If either resistance checks are not as specified, replace TP sensor . Go to step  14.
  4. Turn ignition on. Measure voltage between ground and TP sensor connector terminal No. 4 (Green/Yellow wire). Voltage should be 4.8-5.2 volts. If voltage is as specified, go to step  7. If voltage is not as specified, go to next step.
  5. Turn ignition off. Disconnect PCM connector D-108. Check PCM connector D-108 for loose, damaged, or corroded terminals. If problem exists, repair or replace connector. Go to step  14. If problem does not exist, go to next step.
  6. Check for open or short to ground in Green/Yellow wire between TP sensor connector terminal No. 4 and PCM connector D-108 terminal No. 46. See Figure. If problem exists, repair Green/Yellow wire between TP sensor and PCM. Go to step  14. If problem does not exist, replace PCM. Go to step  14.
  7. Turn ignition off. Check for continuity between ground and TP sensor connector terminal No. 1 (Black wire). If continuity exists, go to step  10. If continuity does not exist, go to next step.
  8. Disconnect PCM connector D-108. Check PCM connector D-108 for loose, damaged, or corroded terminals. If problem exists, repair or replace connector. Go to step  14. If problem does not exist, go to next step.
  9. Check for open or damage in Black wire between TP sensor connector terminal No. 1 and PCM connector D-108 terminal No. 57. If problem exists, repair Black wire. Go to step  14. If problem does not exist, replace PCM. Go to step  14.
  10. Check PCM connectors D-108 and D-109 for loose, damaged, or corroded terminals. If problem exists, repair or replace connector(s). Go to step  14. If problem does not exist, go to next step.
  11. Check for open or short to ground in Yellow/Red wire between TP sensor connector terminal No. 3 and PCM connector D-109 terminal No. 78. If problem exists, repair Yellow/Red wire. Go to step  14. If problem does not exist, go to next step.
  12. Check TP sensor adjustment. See TP SENSOR ADJUSTMENT for ECLIPSE, ECLIPSE SPYDER, GALANT, MONTERO & MONTERO SPORT under THROTTLE POSITION (TP) SENSOR & ACCELERATOR PEDAL POSITION SENSOR in ON-VEHICLE ADJUSTMENTS article. If TP sensor is out of adjustment, adjust TP sensor. Go to step  14. If TP sensor is not out of adjustment, go to next step.
  13. Turn ignition on. Using scan tool, check data list item No. 14 (throttle position sensor). With throttle valve in idle position, voltage should be 0.535-0.735 volt. With throttle valve in fully open position, voltage should be 4.5-5.5 volts. If voltages are as specified, problem is intermittent. See INTERMITTENT DIAGNOSTIC TROUBLE CODES . If voltages are not as specified, replace PCM. Go to next step.
  14. Test drive vehicle following OBD-II drive cycle Other Monitor pattern. See OTHER MONITOR  under OBD-II DRIVE CYCLES under VERIFYING REPAIRS. Check for DTCs. If DTC P0121 is output, go to step  1 and retry diagnostic procedure. If DTC P0121 is not output, inspection is complete.
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