The Trionic T5.2 was introduced in Saab 9000 year 1993 and was discontinued the same year. Its Engine Control Unit is based on a Motorola 32 bit CPU. This engine management system was used on the "long block" engines. Its was superseded by the Trionic T5.5 engine management system. The Trionic T5.2 uses a Mecel patented ion-current measurement to decide which cylinder was in the compression phase and had just ignited the air/fuel mixture. The ion-current measurement is thus used to synchronise the ignition's firing of the spark plug with the cylinder which is full of compressed air/fuel. This ion-current measurement can also determine whether there had been pre-detonation or knocking when the cylinder fired. Finally, the ion-current measurement can be used to identify a misfire with outstanding accuracy.
Trionic T5.2 uses a MAP (Manifold Absolute Pressure) sensor to, indirectly, measure the weight of the air that has been drawn/forced into the cylinders. It uses a simple slotted aperture disc in conjunction with a crank position sensor to identify the Top Dead Center (TDC) for cylinders 1 & 4 and also to measure the engine's RPM.