Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the EVAP vacuum leak pump assembly.
- Ignition OFF, test for less than 10 ohms between the EVAP vacuum leak pump ground circuit terminal 6 and ground G104.
- If greater than the specified range, test the signal low circuit for an open/high resistance. If the circuit tests normal, replace the PCM.
- Connect a test lamp between the EVAP vacuum leak pump control circuit terminal 1 and ground.
- Ignition ON, command the EVAP vacuum leak pump ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If the test lamp does not illuminate, test the leak pump control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the EVAP vacuum leak pump.
- Connect the EVAP vacuum leak pump electrical connector.
- Ensure that the vehicle underbody temperature is similar to the ambient temperature and allow the surrounding air to stabilize before starting the diagnostic procedure. Small changes in fuel tank pressure are difficult to detect with high fuel temperatures.
- Low fuel levels in the fuel tank can affect the accuracy of fuel tank pressure readings. Small changes in fuel tank pressure are detected sooner when the fuel level is between one half and three quarters of a tank.
- Engine running, observe the scan tool FTP sensor voltage parameter. Command the EVAP vacuum leak pump ON and OFF several times with the scan tool. Verify the FTP sensor voltage parameter decreases 0.10-0.20 volts when the pump is activated.
- If less than the specified range, replace the EVAP vacuum leak pump assembly.
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