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Home >> Suzuki >> 2002 >> Aerio GS, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0451: EVAP System Pressure Sensor - Range/Performance >> 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, perform TEST D: ENGINE SYSTEM CHECK  under SYSTEM TESTS then go to next step.
  2. If SUZUKI scan tool or equivalent is not available, go to next step. Turn ignition switch to LOCK position. Open fuel filler cap and turn ignition switch to ON position. Using SUZUKI scan tool or equivalent, check FTP sensor. Fuel tank pressure should be about zero kPa. If pressure displayed on scan tool is not as specified, go to next step. If pressure displayed on scan tool is as specified, go to step  15.
  3. Turn ignition switch to LOCK position. If SUZUKI scan tool or equivalent is not available, open fuel filler cap and turn ignition switch to ON position. Locate ECM harness connector. See Figure. Turn ignition switch to ON position. Backprobe and measure voltage between ground and ECM harness connector G04 terminal No. 22 (Light Green wire). See Figure. If voltage is not 2-3 volts, go to next step. If voltage is 2-3 volts, check ECM and harness connector for poor, loose, corroded or damaged connector terminals. If connector terminals are faulty, repair as necessary and repeat DTC CONFIRMATION TEST . If connector terminals are okay, go to step  15.
  4. Turn ignition switch to LOCK position. Remove fuel tank. See FUEL TANK under FUEL SYSTEM in REMOVAL & INSTALLATION article. Disconnect FTP sensor 4-pin harness connector. See Figure. Check FTP sensor and harness connector for poor, loose, corroded or damaged connector terminals. If connector terminals are faulty, repair as necessary and repeat DTC CONFIRMATION TEST . If connector terminals are okay, turn ignition switch to ON position and measure voltage between ground and FTP sensor harness connector L91 terminal 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.
  5. Turn ignition switch to LOCK position. Remove ECM. See ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION article. Check ECM and harness connectors for poor, loose, corroded or damaged connector terminals. If connector terminals are faulty, repair as necessary and repeat DTC CONFIRMATION TEST . If connector terminals are okay, reconnect ECM harness connectors and turn ignition switch to ON position. Backprobe and measure voltage between ground and ECM harness connector C46 terminal No. 18 (Gray/Red wire). See Figure. If voltage is not 4-6 volts, go to next step. If voltage is 4-6 volts, check for open circuit in Gray/Red wire between FTP sensor, Throttle Position (TP) sensor, Manifold Absolute Pressure (MAP) sensor and ECM. If no open circuit is found, go to next step. If open circuit is found, repair as necessary and repeat DTC CONFIRMATION TEST .
  6. Turn ignition switch to LOCK position. Disconnect TP sensor and MAP sensor harness connectors. See Figure. Turn ignition switch to ON position. Measure voltage between ground and ECM harness connector C46 terminal No. 18 (Gray/Red wire). See Figure. If voltage is not 4-6 volts, go to next step. If voltage is 4-6 volts, check TP sensor and/or MAP sensor for malfunction referring to appropriate DTC test procedure. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . After repair, repeat DTC CONFIRMATION TEST .
  7. Turn ignition switch to LOCK position. Disconnect ECM harness connector C46. See Figure. Turn ignition switch to ON position. Measure voltage between ground and ECM harness connector C46 terminal No. 18 (Gray/Red wire). See Figure. If voltage is zero volts, go to next step. If any voltage is found, check short circuit in Gray/Red wire between FTP sensor, TP sensor, MAP 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 .
  8. Turn ignition switch to LOCK position. Measure resistance between ground and FTP sensor harness connector L91 terminal No. 3 (Gray/Red wire). See Fig 1. If resistance is infinity, go to next step. If any resistance is found, repair short to ground in Gray/Red wire between FTP sensor, TP sensor, MAP sensor and ECM. After repair, repeat DTC CONFIRMATION TEST .
  9. Measure resistance between ECM harness connector C46 terminal No. 18 (Gray/Red wire) and FTP sensor harness connector terminal No. 3 (Gray/Red 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/Red wire between FTP sensor, TP sensor, MAP sensor and ECM. After repair, repeat DTC CONFIRMATION TEST .
  10. Reconnect ECM harness connectors. Measure resistance between ground and FTP sensor harness connector L91 terminal No. 2 (Orange wire). See Fig 1. If resistance is 10 ohms or more, go to next step. If resistance is less than 10 ohms, go to step  12.
  11. Backprobe and measure resistance between ground and ECM harness connector G04 terminal No. 18 (Orange wire). See Figure. If resistance is less than 5 ohms, repair open or short circuit in Orange wire. 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 .
  12. Disconnect ECM harness connector G04. Turn ignition switch to ON position. Measure voltage between ground and ECM harness connector G04 terminal No. 33 (Red/Yellow wire). See Figure. If voltage is zero volt, go to next step. If any voltage is found, check Red/Yellow wire for short to voltage between FTP sensor and ECM. If short circuit is found, repair as necessary and repeat DTC CONFIRMATION TEST . If short circuit is not found, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
  13. Turn ignition switch to LOCK position. Measure resistance between ground and ECM harness connector G04 terminal No. 33 (Red/Yellow wire). See Figure. If resistance is infinity, go to next step. If any resistance is found, repair short to ground in Red/Yellow wire between FTP sensor and ECM. After repair, repeat DTC CONFIRMATION TEST .
  14. Measure resistance between ECM harness connector G04 terminal No. 33 (Red/Yellow wire) and FTP sensor harness connector L91 terminal No. 1 (Red/Yellow 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 Red/Yellow wire between FTP sensor and ECM. After repair, repeat DTC CONFIRMATION TEST .
  15. Perform FTP sensor component test. See FUEL TANK PRESSURE SENSOR under FUEL EVAPORATION under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING article. If FTP sensor is okay, go to next step. If FTP sensor is faulty, replace FTP sensor and repeat DTC CONFIRMATION TEST .
  16. Check the following EVAP system components for a clog: canister, canister air suction filter, canister air suction passage and fuel vapor passage between fuel tank and canister. If any EVAP system component is faulty, repair as necessary and repeat DTC CONFIRMATION TEST . If EVAP system components are okay, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. If intermittent problem is found, repair as necessary and repeat DTC CONFIRMATION TEST . If no intermittent problem is found, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
Fig 1: Identifying Fuel Tank Pressure & Temperature Sensor Harness Connector L91 Terminals
G00232468Courtesy of SUZUKI OF AMERICA CORP.
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