Mercury 4L3Z-12A699-AA Engine Knock Sensor

For 2006 and earlier four-cylinder models, start by disconnecting the cable from the negative battery terminal, then raise the front of the vehicle and secure it on jackstands. Locate the knock sensor on the back side of the block near the alternator; for the 2.3L model, remove the intake manifold first. Detach the knock sensor electrical connector from its bracket and disconnect it, followed by removing the retaining nut and the sensor itself. Installation is the reverse of removal, ensuring the retaining nut is tightened to the specified torque. After reconnecting the battery, the Powertrain Control Module (PCM) must relearn its idle and fuel trim strategy for optimal performance. For 2008 and earlier V6 models, the process begins similarly with the negative battery terminal disconnection and vehicle elevation. The knock sensor is located on the rear side of the block near the transaxle; trace the electrical lead to the connector, disconnect it, and then remove the retaining bolt and sensor. Again, installation is the reverse, with attention to torque specifications. After reconnecting the battery, the PCM must relearn its idle and fuel trim strategy. For 2007 and later four-cylinder models, disconnect the negative battery terminal, remove the intake manifold, disconnect the wiring harness from the sensor, and then remove the mounting bolt and sensor, with installation being the reverse. For 2009 and later V6 models, note that there are two knock sensors; one is on the left end of the rear cylinder head and the other is under the lower intake manifold. Disconnect the negative battery terminal, remove the lower intake manifold if working on the engine block-mounted sensor, disconnect the wiring harness, and remove the mounting bolt and sensor, with installation following the reverse order.

For 4.2L V6 models, the knock sensor is installed in front of the exhaust port on the engine head, in front of the left cylinder. First, pull the negative wire off the battery terminal. To get to the knock sensor, loosen the single bolt which holds the fuel supply line to the transmission bell housing and pull the line out and upward slightly. Lose the electrical connector from the knock sensor, undo the mounting bolt and then pull out the knock sensor. Installation is in the reverse order with a particular emphasis to tightening the knock sensor to the appropriate torque. For 3.5L, 3.7L V6 and all V8 models the knock sensor(s) are located in the valley between the cylinder heads below the intake manifold, which must be removed to get at. Reduce the fuel system pressure and remove the cable of the negative terminal of the battery. Remove the intake manifold. Undo the electrical connector from the knock sensor by pressing down the locking tab; for 5.4L V8 engines, there are two knock sensors with their related connectors; the 4.6L V8 engines only use a knock sensor positioned at the right cylinder head. This involves the removing of the retaining bolt that holds the knock sensor in place on the engine block the knock sensor is then pulled out. Again, installation is the reverse of removal and it is done with an equal torque on the retaining bolt.

To remove, disconnect the battery, remove the intake manifold, disconnect the sensor connector, remove the bolt, and remove the sensor. For 2.7L V6 models, two sensors are located between the cylinder banks and must be replaced together. Next, relieve fuel pressure, disconnect the battery, drain the cooling system, remove the water pump and coolant outlet, remove the fuel rails, disconnect the sensor connector, remove the bolts, and remove the sensors.

In the 4.0L V6 models, the knock sensor is located in the valley between the cylinder heads below the intake manifold, which has to be unbolted to get access to the sensor. First of all, the cable must be disconnected at the negative terminal of the battery. Following the above, rip off the intake manifold. Follow the knock sensor wire back to the sensor's electrical connector and remove it. Turn the knock sensor mounting bolt counter clockwise and pull out the knock sensor. Removal is basically the same to installation, tightening the knock sensor retaining bolt to the required torque. For 3.7L V6, 4.6L and 5.0L V8 engines sensors are located in the valley between the cylinder heads, under the intake manifold and that requires removing the intake manifold to access either of them. These engines are fitted with two knock sensors which are in a single harness and connector and hence must be replaced as a pair. First of all, unscrew the cable from the negative battery connection then take of the intake manifold. Follow the two leads coming from the knock sensors to the electrical connector that joins the two of them and cut that. Loosen the knock sensor retaining bolts, and while on 4.6L V8 engines, the two knock sensors have different electrical leads but are connected to a single electrical connector therefore have to be removed or replaced as a pair. Reinstallation proceeds in the reverse manner to the removal process so as to ensure that knock sensor retaining bolts are tightened to the recommended torque.

For 2006 and earlier four-cylinder models, start by disconnecting the cable from the negative battery terminal, then raise the front of the vehicle and secure it on jackstands. Locate the knock sensor on the back side of the block near the alternator; for the 2.3L model, remove the intake manifold first. Detach the knock sensor electrical connector from its bracket and disconnect it, followed by removing the retaining nut and the sensor itself. Installation is the reverse of removal, ensuring the retaining nut is tightened to the specified torque. After reconnecting the battery, the Powertrain Control Module (PCM) must relearn its idle and fuel trim strategy for optimal performance. For 2008 and earlier V6 models, the process begins similarly with the negative battery terminal disconnection and vehicle elevation. The knock sensor is located on the rear side of the block near the transaxle; trace the electrical lead to the connector, disconnect it, and then remove the retaining bolt and sensor. Again, installation is the reverse, with attention to torque specifications. After reconnecting the battery, the PCM must relearn its idle and fuel trim strategy. For 2007 and later four-cylinder models, disconnect the negative battery terminal, remove the intake manifold, disconnect the wiring harness from the sensor, and then remove the mounting bolt and sensor, with installation being the reverse. For 2009 and later V6 models, note that there are two knock sensors; one is on the left end of the rear cylinder head and the other is under the lower intake manifold. Disconnect the negative battery terminal, remove the lower intake manifold if working on the engine block-mounted sensor, disconnect the wiring harness, and remove the mounting bolt and sensor, with installation following the reverse order.