Diagnosis & Repair (Using OBD-II Scan Tester)
- Check EVAP VSV, vapor pressure sensor VSV and vapor pressure sensor wiring harness connectors for damaged pins, corrosion and loose wires. Repair as necessary. If connectors are okay, go to next step. For component locations, see THEORY/OPERATION article.
- Check all EVAP related vacuum hoses for cracks, looseness and correct routing. Repair as necessary. If vacuum hoses are okay, go to next step. For proper vacuum hose routing, see VACUUM DIAGRAMS article.
- Access ECM behind bottom center of instrument panel, in front of console. Turn ignition on. Backprobing ECM connector, measure voltage between terminals No. 1 (Yellow wire) and No. 9 (Brown wire) at ECM E5 connector. See Figure. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM and retest.
- Backprobing ECM connector, measure voltage between terminals No. 7 (Blue/Yellow wire) and No. 9 (Brown wire) at ECM E5 connector. Disconnect vacuum hose from vapor pressure sensor. Sensor is mounted to center of fire wall in engine compartment. Apply vacuum or pressure to sensor as specified. Voltage reading should be as follows:
- 2.9-3.7 volts with no vacuum applied.
- 4.2-4.8 volts with .22 psi (1.5 kPa) applied.
- 1.3-2.1 volts with .59 in. Hg (2.0 kPa) vacuum applied.
If voltage is as specified, go to step 6). If voltage is not as specified, go to next step.
- Check for an open or short in wiring harness between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace vapor pressure sensor.
- Disconnect EVAP VSV vacuum hoses. VSV is located near charcoal canister. Apply air pressure to VSV port "E". See Fig 1. Air should not exhaust from port "F". Access ECM behind bottom center of instrument panel, in front of console. Turn ignition on. Connect jumper wire between ground and terminal No. 22 (Pink wire) at ECM E4 connector. See Figure. Air should exhaust from port "F". If VSV functions as specified, go to step 8). If VSV does not function as specified, go to next step.
- Check EVAP VSV operation. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS article. Replace VSV as necessary. If VSV is okay, go to next step.
- Check for an open or short in wiring harness between EFI main relay, EVAP VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest.
- Disconnect vapor pressure sensor VSV vacuum hoses. VSV is mounted on top of EVAP charcoal canister. Apply air pressure to VSV port "E". See Fig 2. Air should exhaust from port "G". Access ECM behind bottom center of instrument panel, in front of console. Turn ignition on. Connect jumper wire between ground and terminal No. 8 (Red/White wire) at ECM E5 connector. See Figure. Air should exhaust from port "F". If VSV does not function as specified, go to next step. If VSV functions as specified, check charcoal canister. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS article. Replace canister as necessary.
- Check vapor pressure sensor VSV operation. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS article. Replace VSV as necessary. If VSV is okay, go to next step.
- Check for an open or short in wiring harness between EFI main relay, vapor pressure sensor VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest.