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Home >> Isuzu >> 1997 >> Rodeo LS, 2.6 E >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 2.6L >> Circuit Testing >> DTC P0121 - TP Sensor System Performance >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
  2. Turn ignition on, engine off. Using scan tool, read MAP value. If value is less than 61 kPa, go to next step. If value is 61 kPa or more, go to step 6).
  3. Disconnect MAP sensor harness connector. Connect a test light between MAP sensor harness connector 5-volt reference and signal circuits. Using scan tool, read MAP value. If value is less than 61 kPa, go to step 5). If value is 61 kPa or more, go to next step.
  4. Check MAP sensor signal circuit for open or short between PCM and MAP sensor. If problem is found, repair as necessary. Retest system. If no problem is found, go to step 12).
  5. Replace MAP sensor. Retest system.
  6. Observe scan tool TP ANGLE value while moving throttle from closed to wide open. If value increases steadily and evenly from closed to open throttle, go to DIAGNOSTIC AIDS  . If value does not change as specified, go to next step.
  7. Disconnect TP sensor harness connector. If value is near zero volts, go to next step. If value is not near zero volts, go to step 9).
  8. Connect a test light between TP sensor harness connector 5-volt reference circuit and signal circuit. Using scan tool, read TP sensor voltage. If scan tool voltage is about 5 volts, go to step 11). If voltage is not about 5 volts, go to step 10).
  9. Check TP sensor signal circuit for short to voltage, and ground circuit for high resistance and poor connection. If no problem is found, go to step 12). If a problem is found, repair as necessary. Retest system.
  10. Check TP sensor 5-volt reference circuit for poor connection or high resistance between PCM and TP sensor. If no problem is found, go to step 12). If a problem is found, repair as necessary. Retest system.
  11. Replace TP sensor. Retest system.
  12. Replace PCM. Program replacement PCM using required equipment. Retest system.
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