Er­ror code

Car Mechanics (UK) - - Help! -

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.

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