Knock sensors — replacement Ford F150

Warning: Wait until the engine is completely cool before beginning this procedure.

Note: The knock sensors are located in the valley between the cylinder banks. The knock control system is designed to reduce spark knock during periods of heavy detonation. This allows the engine to use optimal spark advance to improve driveability. The knock sensors detect abnormal vibration in the engine and produce a voltage output which increases with the severity of the knock. The voltage signal is monitored by the PCM, which retards ignition timing until the detonation ceases. A problem in the knock sensor circuit will set a diagnostic trouble code.

Note: All models have two knock sensors that share a single wiring harness; they must be replaced as a pair.

1. Relieve the fuel system pressure (see Fuel and exhaust systems), then disconnect the cable from the negative terminal of the battery (see Engine electrical systems).

2. On 3.5L non-turbo models, disconnect the knock sensor harness electrical connector located on the rear of the left (driver’s side) cylinder head.

3. On 3.3L models, remove the lower intake manifold (see Intake manifold(s) – removal and installation). On 5.0L models, remove the intake manifold (see Intake manifold – removal and installation).

4. On 2.7L and 3.5L models, remove the fuel rails (see Fuel rails and injectors – removal and installation).

5. On 2.7L models, remove the water pump (see Cooling, heating and air conditioning systems) and coolant outlet connector (coolant pipe between the cylinder banks), then disconnect the Engine Coolant Temperature (ECT) sensor connector.

6. On all models, disconnect the electrical connector and remove the bolts securing the knock sensors to the cylinder banks, then remove the knock sensors.

7. Coat the threads of the knock sensor bolts with thread sealant. New sensor bolts are pre-coated with thread sealant; do not apply any additional sealant or the operation of the sensor may be affected.

8. Install the knock sensors and tighten the bolts to the torque listed in this Chapter’s Specifications.

Caution: Do not tighten the knock sensor bolt without a torque wrench. The knock sensor readings may be inaccurate or damage may occur to the knock sensor or engine block.

9. Remainder of installation is the reverse of removal.

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