Examination
1. Knock sensors detect abnormal engine vibration. The engine management system is programmed to control the ignition timing in such a way that the engine runs on the verge of detonation, then at the maximum possible ignition advance. The knock sensors supply an alternating voltage to the input of the BEU, the amplitude of which increases with the intensification of detonation. When a strong detonation occurs, the BEU reduces the ignition timing until the detonation disappears.
2. The knock sensor on a 4-cylinder engine is screwed into the rear (from the side of the engine compartment) stack of cylinder block. On some models, the oil filter must be removed to access the sensor (see chapter 1). On V-engines, the sensor is located under the intake manifold, but the sensor connector is in an accessible area at the end of a long wiring harness, so the manifold will not need to be removed to test the sensor.
3. To check the knock sensor, disconnect its electrical connector and measure the resistance between terminal A and ground (pic. 12.3). The sensor resistance should be about 560 ohms at 20°C. If the resistance is significantly different from the specified value, replace the sensor.
Replacement
Attention! Allow the engine to cool completely before starting this work.
4. Disconnect the negative cable from the battery.
Caution: If your vehicle's audio system is equipped with an anti-theft protection, it will convince the axle that you know its unlock code before disconnecting the battery.
5. Drain the engine coolant (see chapter 1).
6. On a V-shaped engine, remove the intake manifold (see chapter 2B) and coolant pipe.
7. Disconnect the electrical connector from the sensor and remove the sensor (pic. 12.6).
Note. The threads of the new sensor are sealed with sealant, do not overcoat it. Otherwise, the sensor may distort the signal. Screw in the sensor and tighten it securely.
8. Connect the connector to the sensor Fill the engine with coolant and check for leaks. Delete fault codes from the memory of the BEU, if any.