Engine: Engine Knock Sensing System

What it Does

The engine knock sensing system is responsible for “hearing” abnormal engine noise generated by uncontrolled combustion events. You can think of a knock sensor like a little microphone that is bolted to the engine block. If uncontrolled combustion activity is detected, the knock sensing system signals the engine control computer to back off on the ignition timing (in other words, to delay the timing of when each spark plug fires.) Some Hyundai and Kia vehicles are capable of both monitoring for uncontrolled combustion events and also for connecting rod bearing wear (since this bearing wear will also cause internal engine noise.)

Why This Matters

Engine design, condition, operation (speed and engine load), and fuel octane ratings are all relevant to the conditions that can result in abnormal combustion events. A properly operating knock system reduces the odds of internal engine failures caused by the heat and mechanical stresses brought on by abnormal combustion events, and it also helps the engine to run efficiently (with good control of combustion events, which are what generates the engine’s power.) In the case of Hyundai and Kia, this system can also flag a warning before severe internal engine damage results in internal engine destruction. Hyundai and Kia’s usage of this system to monitor for connecting rod bearing wear lowers the odds of you experiencing mechanically-catastrophic engine failure while driving.

Possible Problems

Knock sensing system failure:

Failures can include the knock sensor itself, the computer receiving the sense signals, and the wiring between the two.

Abnormal engine noise:

In some cases, abnormal engine noise can “trick” the knock sensing system into thinking that uncontrolled combustion is occurring, but in reality the noise that the system is “hearing” has nothing to do with combustion activity. Abnormal engine noises can range from more minor concerns (like a bearing knock noise in the belt drive system) to more severe concerns (like engine bearing noise.)

Connecting Rod Bearing Failure (Hyundai & Kia):

Some Hyundai’s and Kia’s use this system to detect connecting rod bearing failure before this failure becomes severe enough to result in mechanically-catastrophic engine failure. Catastrophic engine failure typically includes things that require major service to engine internals or engine replacement, possibly accompanied by loss of power on the road and failure of the engine to restart or run well.