Contents: Examination ⇓ Replacement ⇓
Examination
1. Knock sensors detect abnormal engine vibration. The engine management system is programmed to control the ignition timing so that the engine operates on the verge of detonation, i.e. at the maximum possible ignition timing. Knock sensors supply an alternating voltage to the input of the electronic control unit, the amplitude of which increases with increasing detonation. When severe detonation occurs, the ECU reduces the ignition advance until the detonation disappears.
2. The knock sensor on a 4-cylinder engine is screwed into the rear (from the side of the engine bulkhead) stack of the 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 you don't need to remove the manifold to check the sensor.
3. To check the knock sensor, disconnect its electrical connector and measure the resistance between contact A and ground (figure 12.3). The sensor resistance should be approximately 560 ohms at 20°C. If the resistance differs significantly from the specified value, replace the sensor.
Replacement
Caution: Allow the engine to cool completely before starting this work.
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4. Disconnect the negative cable from the battery.
Caution: If your vehicle's audio system is equipped with anti-theft protection, ensure you know the unlock code before disconnecting the battery.
5. Drain the coolant from the engine (see chapter 1).
6. On a V-engine, remove the intake manifold (see chapter 2B) and the cooling system pipe.
7. Disconnect the electrical connector from the sensor and remove the sensor (figure 12.6).
Note: The threads of the new sensor are coated with sealant, do not apply an extra layer on 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 make sure there are no leaks. Delete the fault codes from the ECU memory, if any are there.