The 12+2home configuration has the same signal pattern as the old 24+TDC configuration from the Toyota. Here there is no CAS but only sensors on the crank and cam directly. The 12 tooth gear gives a pulse every 30 degrees of crank rotation. There are 2 separate Home sensors. Usually one on each cam and they are 360° out of phase. Sometimes they also act as VVTI movement detection sensor. This allows the ECU to sink injection and timing to a specific stroke of the engine every time it starts. This setup requires three inputs from the ECU. The ECU could sync in one revolution. Some ECU’s have only one home input which means then engine may have to turn sometimes two revolutions before crank angle can be established. Below are explanations and also the modifications that could improve stability and simplicity in wiring when using the Spitronics ECU’s.

Using the sensors without modifications is possible but due to the differences in sensors that the Spitronics ECU’s have to cater for, this one needs a bit of external filtering. If your harness has all the wires in one cable, then you need to make an adapter cable from the crank or cam sensor to the other one. They may be far apart so the connecting lead must be screened and the screen wire must be connect to the screen wire of the original loom. Do not connect the screen to the engine. See the drawing below.

Then Crank and Home are connected to P1 pin 12 and 11 respectively. Check the drawings for wire colours. Usually we use only Home1 sensor. You may add the Home2 sensor in parallel to the Home1 sensor. Positives together and reference together. If the sensor signal is strong this will work perfectly. If it is week then it cannot be used. This method is only for Split sequential injection. For full sequential only use Home1 sensor. If you find interference during cranking or at higher revs add the optional resistor A to the circuit. Resistor B is seldom required due to constant excitement of the crank sensor. If it is possible you may grind the teeth under the sensor out when the engine is on TDC and use this with the 12-1 split sequential program. Then you don’t need the cam sensors.