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Home >> Suzuki >> 2001 >> Grand Vitara JLX, 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 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 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 volts 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 volts 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 PCM and go to DTC CONFIRMATION TEST .
  5. Check TP sensor operation. See ENGINE SENSORS & SWITCHES 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 PCM 26-pin connector C51-3 terminals No. 11. See WIRING DIAGRAMS article. Repair as necessary and go to DTC CONFIRMATION TEST . If Gray/Red wire is okay, replace 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 PCM 26-pin connector C51-3 terminals No. 20. See WIRING DIAGRAMS article. Repair as necessary and go to DTC CONFIRMATION TEST . If Gray/Red wire is okay, replace PCM and go to DTC CONFIRMATION TEST .
  8. Check TP sensor adjustment. See THROTTLE POSITION (TP) SENSOR in ON-VEHICLE ADJUSTMENTS article. Adjust as necessary. If TP sensor adjustment is okay, replace PCM and go to DTC CONFIRMATION TEST .
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