Air Injection Check Valve

This procedure covers the removal and replacement of the air injection check valve on the 2018-2024 Honda Accord 1.5L turbo engine to restore proper secondary air injection system function.

Warnings

Tools required

Parts

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

Preparation

1. Ensure engine has been off for at least 45 minutes and exhaust system is cool to touch
2. Disconnect the negative battery terminal and wait 3 minutes to allow capacitors to discharge
3. Raise and secure the front of the vehicle on jack stands if additional access is needed from below
4. Remove the engine cover by pulling up on the four corner clips
5. Spray penetrating oil on all exhaust fasteners that will be removed and allow 10-15 minutes to soak

Procedure

1. 1

   Remove upper heat shield
   Locate the heat shield covering the exhaust manifold area. Remove the heat shield mounting bolts using a 10mm socket. There are typically 3-4 bolts securing the upper heat shield. Carefully remove the heat shield and set aside.
   Torque spec

   Heat Shield Bolts10 Nm (7 lb-ft)
2. 2

   Disconnect air injection hose
   Locate the air injection hose connected to the check valve on the exhaust manifold. Loosen the hose clamp using a flathead screwdriver or 7mm socket. Carefully pull the hose away from the check valve. Inspect the hose for cracks or damage and replace if necessary.
   ℹ️The hose may be brittle from heat exposure. Handle carefully to avoid cracking.
3. 3

   Disconnect electrical connector (if equipped)
   If the check valve has an integrated air pump or sensor, press the locking tab on the electrical connector and disconnect it from the valve assembly. Move the wiring harness out of the way.
4. 4

   Remove check valve mounting bolts
   Using a 12mm or 14mm socket (verify size for your specific valve), remove the bolts securing the air injection check valve to the exhaust manifold. Support the valve with one hand while removing the final bolt to prevent it from falling.
   ⚠If bolts are extremely tight or begin to round, stop and apply additional penetrating oil. Allow to soak and try again to prevent bolt breakage.
   Torque spec

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

   Remove check valve and gasket
   Carefully pull the check valve away from the exhaust manifold. Remove and discard the old gasket. Inspect the mounting surface on the exhaust manifold for damage, warping, or carbon buildup. Clean the mounting surface thoroughly with a gasket scraper and brake cleaner.
6. 6

   Inspect check valve operation
   Before installing the new valve, verify the old valve was faulty by attempting to blow air through it in both directions. Air should flow only in one direction (toward exhaust). If air flows both ways or neither way, the valve was defective. Inspect the new valve for proper one-way operation before installation.
7. 7

   Install new gasket and check valve
   Position the new gasket onto the exhaust manifold mounting surface. Align the new check valve with the mounting holes, ensuring the flow direction arrow points toward the exhaust manifold. Start all mounting bolts by hand to ensure proper thread engagement.
   ⚠Verify the check valve orientation is correct. The arrow on the valve body must point toward the exhaust to prevent reverse flow.
8. 8

   Torque mounting bolts
   Using a torque wrench, tighten the check valve mounting bolts in a cross-pattern to the specified torque. This ensures even pressure on the gasket and prevents leaks.
   Torque spec

   Mounting Bolts26 Nm (19 lb-ft)
9. 9

   Reconnect air injection hose
   Slide the air injection hose onto the check valve inlet port. Ensure the hose is fully seated. Tighten the hose clamp securely, positioning it at least 10mm from the hose end to prevent splitting.
10. 10

    Reconnect electrical connector (if equipped)
    If disconnected earlier, reconnect the electrical connector to the check valve or associated sensor. Ensure the connector clicks into place and the locking tab is fully engaged.
11. 11

    Reinstall heat shield
    Position the upper heat shield back into place. Install and torque the heat shield bolts to specification. Ensure the heat shield is not touching any moving components or electrical wiring.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)

Reassembly

1. Reinstall the engine cover by pressing down firmly on the four corner mounting points until clips engage
2. Reconnect the negative battery terminal and tighten securely
3. If vehicle was raised, lower it safely from jack stands

Verification

• Start the engine and listen for any exhaust leaks near the check valve location. A hissing sound indicates improper gasket seal or loose mounting bolts
• Allow engine to reach operating temperature and verify no unusual noises from the air injection system
• Use a scan tool to check for any air injection system DTCs. Clear codes if present and verify they do not return
• During cold start, listen for proper air injection pump operation (if equipped). The pump should run for 30-60 seconds during initial startup
• Perform a visual inspection after the first drive cycle to ensure no exhaust staining around the check valve, which would indicate a leak

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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