LEMON Manuals: Even more car manuals for everyone
Home >> Suzuki >> 2002 >> Aerio S, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0121: Throttle Position Sensor Circuit - Range/Performance >> Diagnosis & Repair Procedure

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, perform TEST D: ENGINE SYSTEM CHECK  under SYSTEM TESTS then go to next step.
  2. Turn ignition switch to ON position. Using scan tool, observe TP sensor values. TP sensor output voltage with throttle valve completely closed should be 0.2-1.0 volt. And with throttle valve completely open, voltage should be 2.8-4.8 volts. If TP sensor voltage readings are not as specified, go to next step. If TP sensor voltage readings are as specified, go to step  12.
  3. Turn ignition switch to LOCK position. Disconnect TP sensor 3-pin harness connector C29. See Figure. 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, turn ignition switch to ON position. Measure voltage between ground and TP sensor harness connector C29 terminal No. 2 (Gray/Blue wire) and No. 3 (Gray/Red wire). See Fig 1. If voltage is not 4-6 volts, go to next step. If voltage is 4-6 volts, go to step  7.
  4. Turn ignition switch to LOCK position. Locate ECM. See Figure. Disconnect ECM harness connectors, check 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, reconnect ECM harness connectors and disconnect Manifold Absolute Pressure (MAP) sensor 3-pin harness connector. See Figure. Turn ignition switch to ON position. Backprobe and measure voltage between ground and ECM harness connector C46 terminal No. 18 (Gray/Red wire) and No. 25 (Gray/Blue wire). See Figure. If voltage is not 4-6 volts, go to next step. If voltage is 4-6 volts, check Gray/Red wire and Gray/Blue wire for open or short circuit between TP sensor and ECM. Also perform MAP sensor component test. See MANIFOLD ABSOLUTE PRESSURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article. If TP sensor circuits and MAP sensor are okay, go to next step. If TP sensor circuits and/or MAP sensor are faulty, repair TP sensor circuits as necessary and/or replace MAP sensor. See MANIFOLD ABSOLUTE PRESSURE SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL & INSTALLATION article. After repair, repeat DTC CONFIRMATION TEST .
  5. Turn ignition switch to LOCK position. Measure resistance between ground and TP sensor harness connector C29 terminals No. 2 (Gray/Blue wire) and No. 3 (Gray/Red wire). See Fig 1. If resistance is infinity, go to next step. If any resistance is found, check Gray/Blue wire and Gray/Red wire for short to ground between TP sensor and ECM. If short circuit is found, repair as necessary and repeat DTC CONFIRMATION TEST . If no short circuit is found, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
  6. Turn ignition switch to ON position. Measure voltage between ground and TP sensor harness connector C29 terminal No. 2 (Gray/Blue wire) and No. 3 (Gray/Red wire). See Fig 1. If voltage is zero volt, go to next step. If any voltage is found, check Gray/Blue wire and Gray/Red wire for short to voltage between TP sensor and ECM. If short circuit is found, repair as necessary and repeat DTC CONFIRMATION TEST . If no short circuit is found, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
  7. Turn ignition switch to LOCK position. Measure resistance between ECM harness connector C46 terminal No. 25 (Gray/Blue wire) and TP sensor harness connector C29 terminals No. 2 (Gray/Blue wire). See Figure and Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair short circuit in Gray/Blue wire between ECM and TP sensor. After repair, repeat DTC CONFIRMATION TEST .
  8. Reconnect ECM harness connector and ensure proper terminal connection. Also ensure proper terminal connection at MAP sensor. Measure resistance between ground and MAP sensor harness connector C27 terminal No. 2 (Orange wire). See Figure. If resistance is 10 ohms or more, go to next step. If resistance is less than 10 ohms, go to step  10.
  9. Backprobe and measure resistance between ground and ECM harness connector C46 terminal No. 27 (Orange wire). See Figure. If resistance is less than 5 ohms, repair open or short circuit in Orange wire between MAP sensor, TP sensor and ECM. After repair, repeat DTC CONFIRMATION TEST . If resistance is 5 ohms or more, check ECM ground circuits (Black/Orange wire) and (Black wire) for open or short between ECM and ground. If ground circuits are faulty, repair as necessary and repeat DTC CONFIRMATION TEST . If ground circuits are okay, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
  10. Perform TP sensor adjustment. See THROTTLE POSITION SENSOR in ON-VEHICLE ADJUSTMENTS article. After adjustment been performed, measure TP sensor output voltage as in step  2. If voltage is not as specified, go to next step. If voltage is as specified, TP sensor was out of adjustment. After repair, repeat DTC CONFIRMATION TEST .
  11. Turn ignition switch to LOCK position. Disconnect TP sensor harness connector C29 and ensure proper terminal 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 (component side). See Fig 2. See THROTTLE POSITION SENSOR RESISTANCE . If resistances are as specified, go to next step. If any resistance is not as specified, replace TP sensor. See THROTTLE POSITION SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL & INSTALLATION article. After repair, repeat DTC CONFIRMATION TEST .
    THROTTLE POSITION SENSOR RESISTANCE

    Measure Between TP Sensor Terminals No. (1) Specification (K/Ohms)
    1 & 2 0.1-6.5
    1 & 3 4-6
    (1) TP sensor voltage should change slowly and smoothly from low value to high valve as throttle is opened.
  12. Check Mass Air Flow (MAF) sensor performance referring to DTC P0101: MASS AIR FLOW SENSOR - PERFORMANCE PROBLEM . If diagnostic procedures results are okay, go to next step. If diagnostic procedures results are faulty, repair as necessary and repeat DTC CONFIRMATION TEST .
  13. Check throttle body for clog, leak or damage. If throttle body is faulty, replace as necessary. See THROTTLE BODY under AIR INDUCTION SYSTEMS in REMOVAL & INSTALLATION article. After repair, repeat DTC CONFIRMATION TEST . If throttle body is okay, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
Fig 1: Identifying Throttle Position Sensor Harness Connector C29 Terminals
G00232461Courtesy of SUZUKI OF AMERICA CORP.
Fig 2: Testing Throttle Position Sensor
G98A12336Courtesy of SUZUKI OF AMERICA CORP.
scientia non olet · About LEMON Manuals