Selective Injector Cut-Off - Why would that happen; for what reason...

Selective injector cut-off is often employed to protect the engine from certain dangers, such as when overheating. In such cases the ECM intermittently cuts off injector pulse to prevent damage. See how it all fits together here.

 

THEORY OF OPERATION

Selective injector cut-off mode is activated whenever there is a dangerous condition affecting the engine. This is a fairly new feature in fuel control systems designed not only to protect the engine, but the catalytic converter as well. New regulations require manufacturers to guarantee the converter for up to 8 years or 80 K miles. This makes selective injector cut-off a prime feature for catalytic converter protection in case of a misfire. The selective injector cutoff mode is also used in torque management situations where torque reduction is needed. An example is the point when the transmission is shifting gears or the traction control system is activated. In these two examples, torque reduction is needed in order to protect the power train components from sudden high torque conditions. Another need for this operational mode is during high engine temperature conditions, whereby, the fuel injection pulse is cut-off intermittently to four cylinders at a time to prevent the engine from overheating damage. By reducing the cylinder combustion intermittently, the engine generates less heat, saving it from damage.

Selective injector cut-off signal pattern.

 

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