Sunday, March 15, 2015

2004 Jaguar XJ EVAP System: P0442, P0443, P0444, P0445, P0446, P0447, P0448, P0450, P0453, P0453, P0455 and P0456

2004 Jaguar XJ EVAP System

The Evap system on your Jaguar XJ is in charge of recovering the fuel vapors that form on your fuel tank while you drive and while you refill it at the gas station. It consists of:
  • Fuel tank
  • Fuel tank pressure sensor
  • Roll-over valve
  • Charcoal Canister
  • Purge Valve and resonator
  • Canister vent solenoid
  • FTP pump
  • Pipes connecting all the above components
When vapours form in the fuel tank, the car doesn't allow them to go into the atmosphere. They are directed to the Charcoal Canister. This charcoal absorbs these vapours and stores them. When the conditions are right, the computer opens the Canister purge valve and the vacuum of the engine, sucks these vapours into the intake manifold and makes them part of the combustion process that your car uses for power.

The EVAP system has another function, it checks itself for leaks. The EVAP system is designed to protect the environment from fuel vapours, so its logical for it to check itself for problems. The system runs two tests: one while the vehicle is moving and one at idle. While the vehicle is moving the car checks that the Purge Valve is nor stuck neither close nor open and some bigger leaks. While the vehicle is at idle the car checks for really small leaks. These test are run while some conditions are met. These conditions are determined by other parameters on your car: ECT, IAT, engine load, vehicle speed, vapour concentration and purge amount.

The first test (while the vehicle is running): the purge valve closes, and the vent solenoid opens connecting the sealed charcoal canister and fuel tank to the ftp pump. The pump then basically test the system and by creating different pressures while the computer sees the value on the fuel tank pressure sensor. The values have to match certain values inside the program. When this values are not met then codes are set in the computer. Each code description explains what the computer sees.
  • P0442, P0455 big leak detected
  • P0456 small leak detected
  • P0443, P0444, P0445, P0446, P0447, and P0448 purge valve stuck open, close or circuit malfunction.
  • P0450, P0452, and P0453 Fuel tank pressure sensor malfunction
The second test (occurs when the vehicle is at idle stationary or moving at less than 9 mph): this test is basically the same as above but with smaller values, to detect a smaller more precise leak.


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