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 harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 1 (Blue/Red wire) and No. 22 (Brown wire) at ECM E8 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 harness connector, measure voltage between terminals No. 13 (Blue/Yellow wire) at ECM E9 connector and No. 22 (Brown wire) at ECM E8 connector. Disconnect vacuum hose from vapor pressure sensor. Sensor is located in left side of engine compartment, near shock tower. Connect a vacuum pump to sensor. Voltage reading should be as follows:
- 3.0-3.6 volts with no vacuum applied.
- 4.2-4.8 volts with .44 in. Hg (1.5 kPa) applied.
- 1.3-2.1 volts with .59 in. Hg (2.0 kPa) 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. For VSV location, see VACUUM DIAGRAMS article. Apply air pressure to VSV port "E". See Fig 1. Air should not flow from port "F". Access ECM harness connectors behind glove box. Turn ignition on. Connect jumper wire between ground and terminal No. 2 (Yellow/Black wire) at ECM E9 connector. See Figure. Air should flow 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. 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, go to next step.
- 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 flow from port "G". Access ECM harness connectors behind glove box. Turn ignition on. Connect jumper wire between ground and terminal No. 8 (Black/Red wire) at ECM E9 connector. See Figure. Air should flow 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. 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.