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Home >> Suzuki >> 2002 >> Vitara JLS, 2D Utility, 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

NOTE: For better performance and results of this diagnostic procedure, usage of appropriate wiring diagram is recommended. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
NOTE: Perform all voltage and resistance tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use an ohmmeter to isolate wiring harness shorts or opens.
  1. If engine system check has been performed, go to next step. If engine system check has not been performed, see and perform A-4: ENGINE SYSTEM CHECK  under SYSTEM TESTS and go to next step.
  2. Turn ignition switch to ON position. Using scan tool, check for other DTCs related TP sensor. If no other DTCs related to TP sensor are set, go to next step. If DTCs P0122 or P0123 are set, diagnose these DTCs first. See DTC P0122: THROTTLE POSITION (TP) SENSOR CIRCUIT, LOW INPUT  or DTC P0123: THROTTLE POSITION (TP) SENSOR CIRCUIT, HIGH INPUT  . After repair, repeat DTC CONFIRMATION TEST  .
  3. Turn ignition switch to LOCK position. If using scan tool, go to next step. If not using scan tool, locate ECM 26-pin harness connector C51-3 under instrument panel, behind glove box. Turn ignition switch to ON position. Backprobe and measure voltage between ECM harness connector C51-3 terminals No. 9 (Red/Green wire) See Figure . With throttle closed, voltage should be .5-1.2 volts. With throttle fully opened, voltage should be 3.4-4.7 volts. If voltage is not as specified, go to step  5 . If voltage is as specified, check ECM and harness connector terminals for corrosion or poor connection. If connector terminals are faulty, repair as necessary and repeat DTC CONFIRMATION TEST  . If connector terminals are okay, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST  .
  4. Turn ignition switch to ON position and check TP sensor output voltage. Select TP sensor parameter on scan tool. Reading on scan tool with throttle closed should be .5-1.2 volts. Reading on scan tool with throttle fully opened, should be 3.4-4.7 volts. If voltage is not as specified, go to next step. If voltage is as specified, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST  .
  5. Turn ignition switch to LOCK position. Disconnect TP sensor 3-pin harness connector C30, located on throttle body. Check TP sensor and harness connector terminals for corrosion or poor connection. If connector terminals are faulty, repair as necessary and repeat DTC CONFIRMATION TEST  . If connector terminals are okay, measure resistance between TP sensor connector terminals No. 1 and 2 (component test). Resistance should vary linearly according to throttle valve opening between 0.02-6.0 k/ohms. Also measure resistance between TP sensor connector terminals No. 1 and 3, resistance should be 4-6 k/ohms. If any resistance is not as specified, replace TP sensor. See THROTTLE POSITION (TP) SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION article. After repair, repeat DTC CONFIRMATION TEST  . If all resistances are as specified, check for open or short circuit in Gray/Yellow wire, Red/Green wire or Gray/Red wire between ECM and TP sensor. If open or short circuit is found, repair as necessary and repeat DTC CONFIRMATION TEST  . If open or short circuit is not found, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST  .
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