LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Suzuki >> 2001 >> Swift GL, Automatic >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0121: Throttle Position Sensor Circuit Range/Performance Problem >> Diagnosis & Repair Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnosis & Repair Procedure

  1. Perform DTC CONFIRMATION TEST . If DTC P0121 is set, go to next step. If DTC P0121 is not set, problem is intermittent. System is okay at this time. See TROUBLE SHOOTING - NO CODES article.
  2. Check for DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTC P1450 and/or P1451 is also set, repair those DTCs first. See DTC P0450: EVAP SYSTEM PRESSURE SENSOR MALFUNCTION  or DTC P0451: EVAP SYSTEM PRESSURE SENSOR PERFORMANCE  . If DTC P1450 and/or P1451 is not set, go to next step.
  3. If scan toll is not available, go to next step. If scan tool is available, turn ignition on. Using scan tool, check TP sensor output voltage with throttle valve at completely closed and open positions. Go to step  5.
  4. Using voltmeter, backprobe PCM 16-pin connector C22 terminal No. 6 (Light Green/White wire). See Figure. Turn ignition on. Measure voltage between ground and PCM 16-pin connector C22 terminal No. 6 with throttle valve at completely closed and open positions.
  5. Voltage reading should be 0.2-1 volts with throttle valve at closed position and 2.8-4.8 volts with throttle valve at open position. Go to next step. If voltage reading is not within specifications, go to next step. If voltage reading is within specifications and scan tool was used, replace PCM and go to DTC CONFIRMATION TEST . If voltage reading is within specifications and a voltmeter was used, turn ignition off. Disconnect PCM 16-pin connector C22. Check for poor terminal contact at PCM 16-pin connector C22. If poor terminal contact is found, repair as necessary and go to DTC CONFIRMATION TEST . If terminal contact is okay, replace PCM and go to DTC CONFIRMATION TEST .
  6. Turn ignition off. Disconnect TP sensor connector. Check for poor terminal contact at TP sensor connector. If poor terminal contact is found, repair as necessary and go to DTC CONFIRMATION TEST . If terminal contact is okay, measure resistance between specified TP sensor terminals as illustrated. See Fig 1. Go to next step.
  7. Resistance between terminals No. 1 and No. 2 should be 2.5-6 ohms and between terminals No. 1 and No. 3 should be 100-20,000 ohms (depending on throttle angle). If resistance is not as specified, replace TP sensor and go to DTC CONFIRMATION TEST . If resistance is as specified, go to next step.
  8. Check for high resistance in Light Green, Light Green/White or Light Green/Black wires between TP sensor and PCM 16-pin connector C22 terminals No. 1, No. 6 or No. 9. See Figure. Repair suspect wire as necessary and go to DTC CONFIRMATION TEST . If wires are okay, replace PCM and go to DTC CONFIRMATION TEST .
Fig 1: Testing TP Sensor
G98A12336Courtesy of SUZUKI OF AMERICA CORP.
scientia non olet · About LEMON Manuals