Air Injection Check Valve

This procedure covers removal and replacement of the air injection check valve on the 2016-2021 Honda Civic 1.5L turbo engine to restore proper secondary air injection system operation.

Warnings

Tools required

Parts

• Air injection check valve × 1 — Use OEM specification
• Check valve gasket × 1 — Use OEM specification
• Exhaust flange gasket × 1 — Replace if damaged

Preparation

1. Ensure engine is completely cold to the touch
2. Park vehicle on level surface and engage parking brake
3. Disconnect negative battery terminal to prevent accidental engine start
4. Raise front of vehicle and support on jack stands if improved access is needed
5. Apply penetrating oil to all exhaust fasteners and allow to soak

Procedure

1. 1

   Remove engine cover and air intake components
   Remove the plastic engine cover by pulling upward on the pull tabs. Loosen the air intake tube clamps and remove the intake tube for improved access to the exhaust manifold area.
2. 2

   Remove upper heat shield
   Locate and remove the upper exhaust manifold heat shield bolts using a 10mm socket. There are typically 3-4 bolts securing the heat shield. Carefully remove the heat shield to access the check valve area.
   Torque spec

   Heat Shield Bolts10 Nm (7 lb-ft)
3. 3

   Disconnect electrical connectors
   Locate any electrical connectors near the check valve assembly. Press the release tab and carefully disconnect any wiring that may interfere with valve removal. Note routing for reinstallation.
4. 4

   Remove air injection tube connection
   Locate the air injection tube that connects to the check valve. Remove the mounting bolts securing the air tube bracket using a 12mm socket. Carefully disconnect the air tube from the check valve, noting the orientation of any gaskets or seals.
   Torque spec

   Mounting Bolts26 Nm (19 lb-ft)
5. 5

   Remove check valve mounting bolts
   Using a 14mm socket and extension, remove the bolts securing the air injection check valve to the exhaust manifold. Support the valve as you remove the final bolt to prevent it from falling. Remove the valve and old gasket material.
   ⚠Check valve may still be hot even after engine has cooled. Handle carefully and use gloves if necessary.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
6. 6

   Clean mounting surfaces
   Thoroughly clean the exhaust manifold mounting surface using a gasket scraper or wire brush. Remove all old gasket material and carbon deposits. Ensure the surface is completely clean and flat for proper sealing of the new valve.
7. 7

   Install new check valve
   Position the new gasket on the exhaust manifold mounting surface. Apply a thin coat of anti-seize compound to the threads of the mounting bolts. Position the new check valve and start all bolts by hand to ensure proper alignment before tightening.
   ℹ️Verify the check valve is oriented correctly with the airflow direction arrow pointing toward the exhaust manifold.
8. 8

   Torque check valve mounting bolts
   Using a torque wrench, tighten the check valve mounting bolts in a cross-pattern to ensure even pressure on the gasket. Follow the specified torque value to prevent leaks and ensure proper sealing.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
9. 9

   Reconnect air injection tube
   Install a new gasket if equipped, then reconnect the air injection tube to the check valve. Install and tighten the mounting bracket bolts to secure the air tube in position.
   Torque spec

   Mounting Bolts26 Nm (19 lb-ft)
10. 10

    Reinstall heat shield and reconnect components
    Position the upper heat shield back in place and install the mounting bolts. Reconnect any electrical connectors that were disconnected. Reinstall the air intake tube and engine cover.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)

Reassembly

1. Ensure all electrical connectors are fully seated with audible clicks
2. Verify all heat shields are properly positioned and secured
3. Check that no tools or parts were left in the engine bay
4. Reconnect negative battery terminal

Verification

• Start the engine and listen for any exhaust leaks near the check valve area
• Check for diagnostic trouble codes related to the air injection system using an OBD-II scanner
• Allow engine to reach operating temperature and verify no unusual noises from the check valve
• Perform a visual inspection around the valve for any signs of exhaust leaks or smoke
• Test drive the vehicle and verify the check engine light does not illuminate

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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