When knocking occurs, the weight in the cylinder case moves, causing the piezo electric element in the KS to translate the vibration into an electric voltage. A signal is then transmitted from the KS to the ECU. In response, the control unit retards spark timing to prevent engine knocking.
On the Loyale with Multi-Point Fuel Injection (MPFI), the KS is located on top right-side of the cylinder block and senses knock signals from each cylinder.
On the Legacy and Impreza, the KS is installed on top left-side of the cylinder block and senses knock signals from each cylinder.
The SVX is equipped with 2 knock sensors; both are located on top of the cylinder block-one on the right side and one on the left side.
Legacy, Impreza and SVX
See Figure 1
- Disconnect the KS harness.
- Measure the resistance across the KS terminals.
- The resistance should be approximately 560 kilo-ohms.
- Replace the KS if the resistance is out of range.
REMOVAL & INSTALLATION
- Disconnect the negative battery cable.
- Disconnect the KS wire harness.
- Loosen and remove the sensor retainer bolt, then remove the sensor.
- Position the KS on the engine block, and secure in place with the retainer bolt. Tighten the bolt snugly.
- Connect the sensor wire harness.
- Connect the negative battery cable.