2016-2021 Honda Civic Cylinder Head Gasket Warranty Extension

American Honda has released Service Bulletin 26-008, Version 3, dated September 25, 2026, to inform owners and technicians about an extended warranty for the cylinder head gasket on certain 2016-2021 Honda Civic vehicles equipped with the 1.5L Turbo CVT engine. This bulletin supersedes Version 2, which included revisions to the background wording, warranty information, required materials, tool information, and the procedure for determining necessary repairs. The primary goal of this bulletin is to address potential issues where the cylinder head gasket's effectiveness may be reduced, leading to various engine problems.

This warranty extension, identified by TSB 26-008, is a significant measure to ensure customer satisfaction and confidence, covering specific engine conditions that could lead to costly repairs for owners. The extended coverage applies regardless of whether the vehicle has ever been declared a total loss or sold for salvage by a financial institution or insurer, or has a branded or similar title under any state's law, offering broad protection to affected owners.

Symptoms

Owners of affected 2016-2021 Honda Civic models may experience several symptoms indicating a potential Honda Civic cylinder head gasket issue. These include engine overheating, noticeable coolant loss, and engine misfire. These conditions can arise due to the reduced effectiveness of the cylinder head gasket, allowing coolant to leak into the combustion chamber.

Fault Codes / DTCs

In conjunction with the physical symptoms, diagnostic trouble codes (DTCs) P0300 through P0304 may be stored in the vehicle's computer system. These codes typically indicate random or multiple cylinder misfires (P0300) or misfires in specific cylinders (P0301, P0302, P0303, P0304). It is important to note that while these DTCs may be present, they are not a mandatory requirement for the repair under this warranty extension. An ALL DTC check result, with or without these specific codes, is acceptable for warranty claims, provided the other diagnostic criteria are met.

Diagnosis and Trigger Conditions

Diagnosing the Honda Civic cylinder head gasket issue involves a detailed inspection process performed by skilled technicians. The procedure begins with the engine cold and includes running an ALL DTC check using the i-HDS system to document any stored PGM-FI DTCs. The cooling system is then checked for leaks, and a cooling system pressure tester (SVTS272A) is installed after topping off the coolant.

After starting the engine with the climate control off and allowing it to reach normal operating temperature (194°F [90°C]), the cooling system pressure is checked. If the pressure is below 18 psi, it is brought up to 18 psi. All four spark plugs are removed, and a borescope, such as the Snap-on 5.5 mm Borescope (BK5600Dual55 or equivalent), is used to inspect each cylinder for coolant entering at the head gasket. This involves using a 90° camera to scan 360° where the cylinder head meets the block. If coolant is observed, a picture must be taken with the borescope, including the VIN, repair order number, date, and engine number on a sticky note, for warranty claim submission.

Repair Procedure Summary

The corrective action for a leaking cylinder head gasket depends on the extent of the damage, specifically whether the cylinder head or engine block mating surfaces show warpage. Technicians follow Job Aid AJA31119,