This procedure covers the replacement of the knock sensor on the 2018-2024 Honda Accord 1.5L I4 Turbo engine, which is mounted on the engine block below the intake manifold.

Warnings

Tools required

Parts

• Knock sensor × 1 — 30530-RBB-003 or equivalent OEM
• Engine coolant (if drained) × 1 — Honda Type 2 Coolant

Fluids

• Honda Type 2 Coolant (Blue) — 2 qt

Preparation

1. Ensure engine is completely cold to touch
2. Disconnect the negative battery terminal and wait 3 minutes
3. Remove engine cover by pulling upward on four corner clips
4. Place drain pan under vehicle near radiator drain plug
5. Drain approximately 2 quarts of coolant from radiator to lower coolant level below intake manifold

Procedure

1. 1

   Remove air intake system
   Disconnect the mass airflow sensor electrical connector. Loosen the clamp at the throttle body and remove the intake air duct. Remove the air filter box by disconnecting the lower mounting clips and lifting out.
2. 2

   Disconnect throttle body and PCV hoses
   Disconnect the throttle body electrical connector. Disconnect the PCV hose from the intake manifold by squeezing the quick-release clip and pulling straight off. Disconnect any vacuum hoses connected to the intake manifold, noting their positions.
3. 3

   Remove intake manifold mounting bolts and brackets
   Remove the fuel rail mounting bolts using a 10mm socket. Support the fuel rail and move it aside without disconnecting fuel lines. Remove the intake manifold mounting brackets and ground straps. Remove all intake manifold mounting bolts using a 12mm socket, working from outside to center in a crisscross pattern.
   Torque spec

   Mounting Bolts45 Nm (33 lb-ft)
4. 4

   Lift and support intake manifold
   Carefully lift the intake manifold upward and toward the front of the engine. You may need to wiggle it slightly to break the gasket seal. Support the manifold on the engine bay frame or rest it on protective shop rags. Do not fully remove it unless necessary as coolant hoses may still be attached.
5. 5

   Locate knock sensor
   The knock sensor is located on the engine block, below where the intake manifold was positioned, typically on the exhaust side of the block. It will have a single wire connector with a locking tab. Clean any debris from around the sensor area before proceeding.
6. 6

   Disconnect knock sensor electrical connector
   Press the locking tab on the knock sensor connector and pull straight away from the sensor. Do not pull on the wire itself. Inspect the connector for corrosion or damage.
7. 7

   Remove knock sensor
   Using a 12mm deep socket with extension, carefully remove the knock sensor bolt. Turn counterclockwise until the sensor is free. Remove the sensor from the engine block. Note the orientation and position of any washers or spacers.
   ⚠The sensor threads may be coated with thread sealer. Do not force removal; apply gentle back-and-forth rotation if stuck.
   Torque spec

   Knock Sensor20 Nm (15 lb-ft)
8. 8

   Clean sensor mounting surface
   Clean the knock sensor mounting boss on the engine block with a clean rag. Remove any old thread sealer or corrosion. The mounting surface must be clean and flat for proper sensor operation. Do not use solvents that could contaminate the coolant passages.
9. 9

   Install new knock sensor
   Apply a small amount of anti-seize compound to the sensor threads if desired (not required on OEM sensors with pre-applied coating). Thread the new knock sensor into the engine block by hand until finger-tight, ensuring it starts straight. Using a torque wrench and 12mm socket, tighten the knock sensor to exactly 20 Nm (15 lb-ft). Do not over-torque.
   ⚠Torque specification is critical. Over-torquing will damage the sensor and under-torquing will cause false knock detection.
   Torque spec

   Knock Sensor20 Nm (15 lb-ft)
10. 10

    Reconnect knock sensor connector
    Push the electrical connector onto the knock sensor until the locking tab clicks into place. Verify the connection is secure by gently tugging on the connector body (not the wire).
11. 11

    Install intake manifold
    Inspect the intake manifold gasket for damage and replace if necessary. Clean the mating surfaces on both the manifold and cylinder head. Position the intake manifold back onto the cylinder head, ensuring all gaskets are properly aligned. Install all mounting bolts finger-tight first, then torque in a crisscross pattern from center outward to 26 Nm (19 lb-ft).
    ⚠Ensure intake manifold gasket is properly seated to prevent vacuum leaks.
    Torque spec

    Mounting Bolts45 Nm (33 lb-ft)
12. 12

    Reinstall fuel rail and accessories
    Reposition the fuel rail and install mounting bolts to specification. Reconnect all vacuum hoses and PCV hose in their original positions. Reconnect the throttle body electrical connector.
13. 13

    Reinstall air intake system
    Install the air filter box and secure lower mounting clips. Connect the intake air duct to the throttle body and tighten the clamp. Reconnect the mass airflow sensor electrical connector.
14. 14

    Refill coolant and check for leaks
    Refill the cooling system with Honda Type 2 Blue coolant to the proper level. Reconnect the negative battery terminal. Start the engine and allow it to reach operating temperature while monitoring for coolant leaks around the intake manifold. Check coolant level again after engine reaches operating temperature and add if necessary.

Reassembly

1. Ensure all electrical connectors are fully seated and locked
2. Verify all vacuum hoses are properly reconnected
3. Double-check that all intake manifold bolts are torqued to specification
4. Reinstall engine cover by pressing down on all four corner clips until they click
5. Top off coolant reservoir to FULL COLD mark after engine has cooled

Verification

• Start the engine and verify it idles smoothly without misfires or rough running
• Use a scan tool to verify no diagnostic trouble codes are present, particularly P0325 (knock sensor circuit) or P0327 (knock sensor low input)
• Monitor coolant temperature and ensure no overheating occurs
• Check for coolant leaks around intake manifold gasket areas
• Perform a test drive and verify normal engine operation under light and moderate acceleration
• Clear any learned knock sensor adaptation values using a scan tool if available, to allow ECU to relearn with new sensor

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