It always seems like in late spring or late fall, when we have those wide variations in temperature, it seems that these two codes always pop up, P0456 and P0442. Both of these codes indicate that there is a leak in the evaporative emission system.
So how does the system test for a leak? Is it a camera that goes around the tank? Do they pump it full of pressure? No, they actually use vacuum.
So how does the EVAP system generate a vacuum if it doesn’t have a vacuum pump on the tank? Well, the simple answer is temperature. If it seals off the system and allows the fuel and the tank to cool, it contracts. When it contracts, it creates a vacuum.
This vacuum, well, it’s sensed by the pressure sensor inside the tank. If the vacuum is lost, it knows it has a leak. But if the vacuum stays constant and where it should be, it knows that the system is sealed.
To do this, well, it’s got to know the outside temperature. It’s got to have a certain level of fuel in it, and it has to be parked for a certain amount of time. This way, it can complete the monitor, and you know that the system is sealed and you’re not going to get those codes for P0456 or P0442.
So it’s critical that the sensor works properly. And especially during this time of year when June, or let’s say October, where we have these wide fluctuations in temperature, clear the code, make sure the customer knows the criteria for carrying out the monitor. This way, you can be sure where the leak is.
I’m Andrew Markel. Thank you very much.
This video is sponsored by Auto Value and Bumper to Bumper.
