ST225 Sensor Pack

All of these sensors are (O.E.M) Ford parts Made by Bosch and pierburg.

• The map (Manifold Absolute Pressure) sensor is a very important sensor on the ST225, this component is responsible for monitoring and reporting back to the ecu variances in pressure / boost. This part is located just after the intercooler and is mounted in the charge pipe just before the inlet.
• The MAF seems to be a very common item to change out on the ST225 as it seems to get contaminated quite quickly by dirt or performance filters which are over oiled and hence coat the MAF.

The job of the Mass Air Flow sensor is to detect the volume, temperature and density of the air passing through it. This information is then relayed to the ecu so the fuel trims can be commanded to make the correct mixture for the exact volume of air being received. When the MAF is faulty, dirty or faulty it will not usually see the correct air volume and the car will either over or under fuel and can cause a lumpy idle and in certain cases an esp fault can appear on the dashboard.

• The boost control solenoid on the Ford Focus ST225 is located behind the turbo and is responsible for controlling the turbo actuator through the varying stages of commanded boost.

The solenoid itself is manufactured by Pierburg and is found to be a very reliable and maintenance free component, however if you are experiencing problems with your commanded boost or any lumpiness when coming on or off the throttle this may be the culprit and certainly worth changing, especially on vehicles running heavy mods.

We have found from performing diagnostics on hundreds of these cars over the years that there are 3 common sensors which tend to be responsible for the majority of poor running issues and lack of power and even esp system faults. These would be

Mass AirFlow sensor > MAF
Manifold Absolute Pressure Sensor > MAP
Boost Control Solenoid. > TCV

These 3 sensors all communicate with each other, the MAF first records and reports the characteristics of the air passing through it, the boost solenoid commands a set boost and the MAP sensor then calculates what boost pressure should be received after the turbo in the charge system. We do recommend on vehicles which are 3 years old or older that have never changed these sensors to do so to restore your vehicles lost performance, driveability and responsiveness it would by now have lost.

*all recommendations are from vehicle observation and are not irrefutable to solving faults, these are simply guidelines*