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Home >> Suzuki >> 2002 >> Esteem GL, 4D Sedan, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - 1.8L >> Diagnostic Tests >> DTC P0121: Throttle Position Sensor Circuit - Range/Performance Problem >> Diagnosis & Repair Procedure
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Diagnosis & Repair Procedure

  1. If engine system check has been performed, go to next step. If engine system check has not been performed, go to A4: ENGINE SYSTEM CHECK  under SYSTEM TESTS.
  2. If scan tool is not available, go to next step. If scan tool is available, turn ignition on. Using scan tool, observe and note TP sensor output voltage with throttle valve at completely closed and open positions. Voltage reading should be 0.35-.65 volts with throttle valve at closed position and 3.5-4.5 volts with throttle valve at open position. TP sensor voltage should change slowly and smoothly from low value to high valve as throttle is opened. If output voltage is not as specified, go to step  6 . If output voltage is as specified, substitute a known good ECM, and repeat DTC CONFIRMATION TEST  .
  3. Turn ignition on. Backprobing at ECM, measure voltage between ground and ECM harness connector C20 terminal No. 25 (Gray wire) with throttle valve at completely closed and open positions. See Figure . Voltage reading should be 0.35-.65 volts with throttle valve at closed position and 3.5-4.5 volts with throttle valve at open position. TP sensor voltage should change slowly and smoothly from low value to high valve as throttle is opened. If voltage reading as specified, go to next step. If voltage reading is not as specified, check for poor terminal contact at ECM harness connector C20. If problem is found, repair as necessary. After repair, repeat DTC CONFIRMATION TEST  . If no problem is found, substitute a known good ECM, and repeat DTC CONFIRMATION TEST  .
  4. Check intake system for plugging and vacuum leaks. If problem is found, repair as necessary. If intake system is okay, turn ignition off. Disconnect ECM 28-pin harness connector C20. ECM is located under instrument panel, behind glove box. See Figure . Check for poor terminal contact at ECM harness connector C20. If problem is found, repair as necessary. After repair, repeat DTC CONFIRMATION TEST  . If no problem is found, go to next step.
  5. Substitute a known good ECM, and repeat DTC CONFIRMATION TEST  .
  6. Adjust TP sensor. See THROTTLE POSITION SENSOR in ON-VEHICLE ADJUSTMENTS article. Recheck TP sensor operation. If TP sensor operation is still not okay, go to next step.
  7. Turn ignition off. Disconnect TP sensor 3-pin harness connector. Check for poor terminal contact at TP sensor connector. If poor terminal contact is found, repair as necessary. After repair, repeat DTC CONFIRMATION TEST  . If no problem is found, go to next step.
  8. Measure resistance between specified TP sensor terminals. See CHECKING THROTTLE POSITION SENSOR RESISTANCE  table. See Fig 1 . If resistance is as specified, go to next step. If resistance is not as specified, replace TP sensor. After repair, repeat DTC CONFIRMATION TEST  .
    CHECKING THROTTLE POSITION SENSOR RESISTANCE

    Measure Between TP Sensor Terminals No. (1) Specification (K/Ohms)
    1 & 2 .1-6.5
    1 & 3 4-6
    (1) TP sensor voltage should change slowly and smoothly from low value to high valve as throttle is opened.
  9. Substitute a known good ECM, and repeat DTC CONFIRMATION TEST  . If DTC does not reset, testing is complete.
Fig 1: Testing Throttle Position Sensor
G98A12336Courtesy of SUZUKI OF AMERICA CORP.
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