Error Codes: if the led flashes and displays error codes C6, C6L, C6H and E4 error, the pressure sensor is faulty; in most cases this is due to build-up on the sensor contacts; cleaning the contacts will solve the problem; if the problem is still not solved, it's time for a new pressure sensor.
How to test a new pressure sensor replacement: add 3 cups of water to the pressure cooker and set it to high pressure for 5 minutes; if the emergency vent starts to leak or vent during heat cycling, the pressure in the can is too high; unplug it immediately and release it quickly; after 5 minutes, empty it using the quick-release device; it should release the pressure vigorously; if it doesn't, the pressure cooker isn't getting enough pressure.