What does it mean?
P1494 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: EVAP Ventilation Switch Circuit Malfunction .
Symptoms
- MIL on
- EVAP monitor fails or never completes
- Fuel filling problems, with the nozzle shutting off early if the vent stays closed
- Fuel vapour odour around the rear of the vehicle
- A hiss or rush of air when the fuel cap is opened, from tank pressure or vacuum
- Engine drivability is normally unaffected
Likely causes
- Failed EVAP vent valve or its integrated ventilation switch
- Open or shorted signal circuit between the switch and the module
- Corroded connector near the charcoal canister, exposed to road spray and salt
- Vent valve contaminated with dust or water and stuck in one position
- Underbody harness damaged by road debris or rodents
- Poor ground for the switch circuit
- Module input driver fault
How to fix it
- Command the vent valve with a scan tool and watch the switch signal change state
- Inspect the connector and harness at the canister for corrosion and impact damage
- Check continuity of the signal circuit from the switch back to the module
- Test the vent valve for free flow when open and for a full seal when closed
- Look for dirt, water or debris blocking the vent path and the canister filter
- Replace the vent valve or switch if it does not respond, or repair the wiring
- Clear the code and complete an EVAP monitor run to verify