Don't know personally, but found this online:
P1494 Leak Detect Pumps SW or mechanical fault
Leak Detection Pump (LDP) switch operation is monitored immediately after a cold start, with ambient temperature 40-90 degrees F and engine coolant temperature within 10 degrees F of ambient temperature. DTC will set in Powertrain Control Module (PCM) memory when PCM does not sense a change in switch state when LDP solenoid is energized.
Possible causes are:
- Leak or obstruction in LDP vacuum supply.
- Defective LDP.
- LDP switch senses circuit open, shorted, corroded or defective PCM. The switch connector is a very common problem.
So it seems the code is set at startup, when certain temperature parameters are met - which may be why the dealership said it's ok to drive.
Also, there's a really good article about it
HERE.