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Home >> Mitsubishi >> 2002 >> Mirage LS, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - 1.8L >> Diagnostic Tests >> DTC P0121: Throttle Position Sensor Circuit Range/Performance Problem >> Diagnostic Procedure
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Diagnostic Procedure

NOTE: After repairs, verify repair by driving vehicle according to appropriate monitor drive cycle and check for DTCs. See VERIFYING REPAIRS  .
  1. Turn ignition on. Using scan tool, check data list item No. 14 (TP SENSOR). With throttle in idle position, voltage should be .3-1.0 volt. With throttle in fully open position (wide open throttle), voltage should be 4.5-5.5 volts. If voltages are not as specified, go to next step. If voltages are as specified, problem is intermittent. See INTERMITTENT DIAGNOSTIC TROUBLE CODES  .
  2. Turn ignition off. Disconnect TP sensor 4-pin connector. Measure resistance between TP sensor connector terminals No. 1 and 4 (component side). See Figure . Resistance should be 3.5-6.5 k/ohms. Measure resistance between TP sensor connector terminals No. 2 and 4 (component side) while slowly opening throttle. Resistance should change smoothly in proportion to throttle opening. If neither resistance is as specified, replace TP sensor. If both resistances are as specified, go to next step.
  3. Turn ignition on. Measure voltage between ground and TP sensor harness connector terminal No. 1 (Green/Blue wire). Voltage should be 4.8-5.2 volts. If voltage is as specified, go to next step. If voltage is not as specified, go to step  6 .
  4. Turn ignition off. Check continuity between ground and TP sensor harness connector terminal No. 4 (Black wire). Continuity should exist. If continuity is as specified, go to next step. If continuity is not as specified, go to step  6 .
  5. Connect TP sensor connector. Turn ignition on. Backprobing, measure voltage at Green/White wire between ECM connector B37 terminal No. 84 (M/T), or PCM connector B75 terminal No. 78 (A/T) and ground. Voltage should be 0.3-1.0 volt with throttle valve at idle position and 4.5-5.5 volts with throttle valve fully open. If voltage is not as specified, check TP sensor connector for damage or looseness. Repair as necessary. If connector is okay, repair Green/White wire between TP sensor and ECM (M/T) or PCM (A/T). See WIRING DIAGRAMS article. If voltage is as specified, check ECM connector B37 (M/T) or PCM connector B75 (A/T) for damage or looseness. Repair connector as necessary. If connector is okay and problem still exists, replace ECM (M/T) or PCM (A/T).
  6. Check ECM connector B37 (M/T) or PCM connector B75 (A/T) for damage or looseness. Repair connector as necessary. If connector is okay and problem still exists, check for opens, shorts or poor connections between TP sensor and ECM harness connector B37 (M/T) or PCM harness B75 (A/T). See WIRING DIAGRAMS article. Repair connector or wiring as necessary. If connector and wiring is okay, replace ECM (M/T) or PCM (A/T).
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