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Home >> Suzuki >> 2002 >> Grand Vitara JLS, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0121: Throttle Position (TP) Sensor Circuit Performance Problem >> Diagnosis & Repair Procedure
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Diagnosis & Repair Procedure

  1. Check for DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0122, P0123, P0335 and P1451. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If DTCs are not set, go to next step. If any DTC is set, go to that test first.
  2. 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 INTERMITTENTS TROUBLE SHOOTING - NO CODES article.
  3. Start engine and allow to reach normal operating temperature. Turn ignition off. Turn ignition on. Backprobing, measure voltage between ECM (PCM) 26-pin connector C51-3 terminals No. 12 (Red/Green wire) and No. 20 (Gray/Yellow wire). See Figure . Measure voltage with throttle in closed and fully open positions. If readings are .35-.65 volt with throttle in closed position and 3.5-4.5 volts with throttle in fully open position, go to next step. If readings are not .35-.65 volt with throttle in closed position and 3.5-4.5 volts with throttle in fully open position, go to step  5 .
  4. Visually inspect for any obstructions or leaks in air intake system ducting. Repair as necessary and go to DTC CONFIRMATION TEST  . If air intake system checks okay, replace ECM (PCM) and go to DTC CONFIRMATION TEST  .
  5. Check TP sensor operation. See ENGINE COOLANT TEMPERATURE SENSOR in SYSTEM & COMPONENT TESTING article. Replace as necessary and go to DTC CONFIRMATION TEST  . If TP sensor is okay, go to next step.
  6. Disconnect TP sensor connector. Measure voltage between ground and TP sensor harness connector terminal No. 3 (Gray/Red wire). If 4.5-5.5 volts exist, go to next step. If 4.5-5.5 volts do not exist, check for short or open in Gray/Red wire between TP sensor and ECM (PCM) 26-pin connector C51-3 terminals No. 11. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary and go to DTC CONFIRMATION TEST  . If Gray/Red wire is okay, replace ECM (PCM) and go to DTC CONFIRMATION TEST  .
  7. Check continuity between ground and TP sensor harness connector terminal No. 1 (Gray/Yellow wire). If continuity exists, go to next step. If continuity does not exist, check for open in Gray/Yellow wire between TP sensor and ECM (PCM) 26-pin connector C51-3 terminals No. 20. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary and go to DTC CONFIRMATION TEST  . If Gray/Red wire is okay, replace ECM (PCM) and go to DTC CONFIRMATION TEST  .
  8. Check TP sensor adjustment. See THROTTLE POSITION SENSOR in ON-VEHICLE ADJUSTMENTS article. Adjust as necessary. If TP sensor adjustment is okay, replace ECM (PCM) and go to DTC CONFIRMATION TEST  .
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