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.
- 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.
- 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 4-6 volts, go to next step. If voltage is not 4-6 volts, repair open circuit in Gray/Red wire between FTP sensor, Throttle Position (TP) sensor, Manifold Absolute Pressure (MAP) sensor and ECM. After repair, repeat DTC CONFIRMATION TEST .
- 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 to voltage is found, repair as necessary and repeat DTC CONFIRMATION TEST . If short to voltage is not found, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
- 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, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST . If FTP sensor is faulty, replace FTP sensor and repeat DTC CONFIRMATION TEST .