I had the error code ‘PO444’ on my 2006 Ford Focus 1.6 Ghia fivedoor, so I changed the purge valve under the bonnet and cleared the code, but the warning light is still illuminated. I am unclear how the evaporative control system works, but I understand there must be a pressure sensor somewhere, presumably along with a one-way valve to allow air to take the place of the used fuel. Any help you can give with the locations of these components would be much appreciated. Joe Sykes The fuel vapour evaporation system is quite simple, consisting of the purge valve (which you have already replaced) and an evaporation emission canister. The canister is connected to the fuel tank via a combination of rubber and plastic hoses, and the purge valve is connected to the inlet manifold. The valve is controlled directly by the Powertrain Control Module (PCM) using a set calibrated table of operation. The normal position for the purge valve is closed and the fuel tank vents through the canister, which absorbs the hydrocarbon emissions from the fuel tank. When the valve is open, the canister is subjected to the manifold depression and the vapour deposits are drawn into the inlet manifold to mix with the combustion mixture.
The code ‘P0444’ indicates that the purge control circuit is open. As you have replaced the valve, this leaves the wiring and connections. First, I would ensure that there are no breaks in the loom and that the connecting plugs to both the valve and PCM are in a good, clean condition.
The terminal from the PCM is number F16. Looking at the PCM with the plug removed, you will see two distinct banks of terminals: one has 52 terminals and the other 42. With the smaller bank of terminals to your right, there should be four larger terminals at the top right. Starting at the left and counting from the top row of the left bank, terminal F16 will be around the centre of the second row down. Having located the terminal, you can use an ohmmeter to check the continuity between this and the valve. If no wiring problems are found, the fault may be within the PCM.