Vapor Pressure Sensor Circuit

1. Turn ignition off. Disconnect vapor pressure sensor connector. Vapor pressure sensor is located in left front of engine compartment. Measure voltage between Blue/Red wire and Brown wire at vapor pressure sensor harness connector.
2. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, check wiring harness between sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM.
3. Reconnect vapor pressure sensor connector. Access ECM behind glove box. Backprobing ECM harness connector, measure voltage between terminals No. 18 (Pink/Green wire) at ECM E11 connector and No. 22 (Brown wire) at ECM E13 connector. See Figure. Go to next step.
4. Disconnect vacuum hose from vapor pressure sensor. Voltage reading should be as follows:
   • 3.0-3.6 volts with no vacuum applied.
   • 1.3-2.1 volts with .59 in. Hg (2.0 kPa) of vacuum applied.
   • 4.2-4.8 volts with .22 psi (1.5 kPa) of pressure applied.

If voltage is not as specified, replace vapor pressure sensor.