Knock sensors

How you know it is this

• A knock sensor fault code
• Loss of power, because the engine has retarded the timing as a precaution
• Heavy fuel consumption with no other symptom

Worth knowing before you buy

• A failed sensor makes the engine run permanently retarded and safe, which costs power and fuel without any obvious noise.
• Torque on fitting genuinely matters — too loose or too tight and the sensor cannot hear properly and reads as faulty.
• Usually buried under the inlet manifold, so the part is cheap and the access is not.
• Poor fuel quality causing real knock will throw the same code with a perfectly good sensor.

Rest of the ignition

• Spark plugs
• Ignition coils and coil packs
• HT leads
• Distributor cap and rotor arm
• Ignition control module / amplifier
• Glow plugs (diesel)
• Glow plug control module
• Ignition switch and lock cylinder