NHTSA ID Number: 11022041
Manufacturer Communication Number: A25-062
TSB/Document Date: 2025-08-21
Summary
Service Bulletin - Water could enter the hood scoop and accumulate down inside the no. 4 spark plug hole. This can corrode the ignition coil, plug tube, and spark plug, leading to a misfire to the no. 4 cylinder. If a misfire is detected, DTC P0304 is stored.
Service Bulletin
August 19, 2025
25-062
Version 1
Misfire No. 4 Cylinder (DTC P0304)
APPLIES TO
Year
Model
Trim Level
2017–21
Civic
TYPE R
VIN Range
ALL
SYMPTOM
The MIL comes on with stored DTC P0304, No. 4 Cylinder Misfire detected.
POSSIBLE CAUSE
Water could enter the hood scoop and accumulate down inside the no. 4 spark plug hole. This can corrode the ignition coil,
plug tube, and spark plug, leading to a misfire to the no. 4 cylinder. If a misfire is detected, DTC P0304 is stored.
Honda
has redesigned the cylinder head cover that will divert water away from the no. 4 spark plug hole and ignition coil if
any water should enter through the hood scoop.
CORRECTIVE ACTION
Inspect the no. 4 cylinder spark plug base for water accumulation and/or corrosion around the spark plug tube.
• If corrosion or water is found, replace the cylinder head cover, spark plug, and ignition coil.
• If corrosion on the plug tube is excessive (12 mm or more), photo submission of excessive rust corrosion is required.
• If no water or corrosion is found, this service bulletin does not apply. Continue with normal troubleshooting.
WARRANTY CLAIM INFORMATION
Operation
Number
Description
Flat Rate
Time
Defect
Code
Symptom
Code
Template
ID
1100B2
Repair Procedure A:
Inspect #4 ignition
coil, spark plug & plug
tube. Clean plug tube
and reinstall the
cylinder cover.
(Includes DTC clear)
1.4hr
00801
03203
A25062A
Repair Procedure B:
Replace cylinder head
(includes inspection,
DTC clear, idle learn &
photos)
13.6hr
1105E1
Failed Part Number
10003-RPY-G01
00801
03203
A25062B
NOTE: For Repair Procedure B, photo submission of excessive rust corrosion/hole(s)/crack(s) on the plug tube
is required. Provide photos of the VIN plate and the damaged plug tube. Photos should be clear and in focus, or
the claim may be subject to a debit.
CUSTOMER INFORMATION: The information in this bulletin is intended for use only by skilled technicians who have the proper tools, equipment,
and training to correctly and safely maintain your vehicle. These procedures should not be attempted by “do-it-yourselfers,” and you should not
assume this bulletin applies to your vehicle, or that your vehicle has the condition described. To determine whether this information applies, contact
an authorized Honda automobile dealer.
© 2025 American Honda Motor Co., Inc. – All Rights Reserved
Page 1 of 6
PARTS INFORMATION
Repair Procedure A (cylinder head cover, ignition coil, and spark plug replacement)
Part Name
Part Number
Quantity
Cover Assy., Cylinder Head
12310-5BA-A01
1
Rubber set, Breather
17136-5BF-A00
1
O-ring (10.2 x 1.8)
91307-RCA-A01
1
O-ring (14.8 x 1.8) (NOK)
91308-RCA-A01
1
Coil Assy., Plug Top (Ignition Coil)
30520-59B-023
1
Spark plug (ILZKAR8H8S) (NGK)
12290-59B-003
1
Repair Procedure B (cylinder head remove and replace)
Part Name
Part Number
Quantity
Cover Assy., Cylinder Head
12310-5BA-A01
1
Rubber Set, Breather
17136-5BF-A00
1
O-ring (10.2 x 1.8)
91307-RCA-A01
1
O-ring (14.8 x 1.8) (NOK)
91308-RCA-A01
1
Coil Assy., Plug Top (Ignition Coil)
30520-59B-023
1
Spark plug (ILZKAR8H8S) (NGK)
12290-59B-003
1
Nut, Self-Lock (10 mm)
90012-59B-004
4
Gasket Kit, Cyl. Head
06110-RPY-G02
1
Gasket, Turbocharger Pipe
19524-RPY-G01
1
Pipe Set, Fuel Joint
16012-RPY-315
1
96600-06020-18
2
Pipe, Fuel Feed
16013-RPY-305
1
Clip, Injector
16451-RPY-G01
4
91310-RPY-G01
4
Disk, Supporting
91312-RPY-G01
4
Washer, Sealing (20 mm)
12209-PR3-000
2
General Assy., Cylinder Head
10003-RPY-G01
1
Page 2 of 6
REQUIRED MATERIALS
Procedure A
Part Name
Hondabond HT
Burgandy colored abrasive pad
Part Number
Quantity
08718-0004
1
(services 20 vehicles)
commercially available
1
Procedure B
Part Name
Part Number
Quantity
Hondabond HT
08718-0004
1
Honda Long-Life Antifreeze/Coolant Type 2
0L999–9011
3 gallons
TOOL INFORMATION
Tool Name
Guide, Valve Cover (Set)
Part Number
07AAG-RPYA100
Quantity
1
Page 3 of 6
INSPECTION PROCEDURE
1. Connect HDS to the DLC. (Click HERE)
2. Verify DTC P0304 is stored.
3. Remove the engine cover and remove the no. 4 ignition coil. (Click HERE)
4. Inspect cylinder no. 4 spark plug tube, remove any residual water from the plug tube area.
5. Remove cylinder no. 4 spark plug and inspect for any corrosion on the plug.
6. Remove the remaining ignition coils.
7. Remove the cylinder head cover. (Click HERE)
8. Inspect cylinder no. 4 ignition coil, plug tube, and spark plug of residual water and corrosion.
Are there any signs of water and/or corrosion on the ignition coil, plug tube, or spark plug?
Yes – Go to step 9.
No – This bulletin does not apply, continue with normal troubleshooting.
9. Place a clean shop towel around the bottom of the no. 4 spark plug tube, then clean the excessive rust and corrosion
from the spark plug tube using a burgundy colored abrasive pad.
10. After cleaning the rust and corrosion:
• Check the spark plug tube for small holes and/or cracks
• Place the seal guide on to the no. 4 spark plug tube
Does the corrosion on the no. 4 spark plug tube exceed 12 mm or extend beyond the bottom of the seal tube guide?
Are there small holes and/or cracking in the tube?
Yes – Take a photo of the spark plug tube corrosion/hole(s)/crack(s), then proceed to Repair Procedure B.
No – Go to Repair Procedure A.
Page 4 of 6
REPAIR PROCEDURE A
New Cylinder Head Cover, Ignition Coil, and Spark Plug Replacement
1. Install the seal tube guide tool on top of the clean no. 4 cylinder plug tube.
NOTE: Make sure the tapered end of the seal tube guide tool is pointing up.
2. Apply a light coat of fresh engine oil to the new head cover plug seal, then carefully slide the head cover over the seal
tube guide and onto the cylinder head.
3. Set the seal tube setter tool in the head cover and on top of the seal tube guide. Make sure the plug tube is properly
set in the cylinder head cover.
Page 5 of 6
4. Remove the seal tube setter tool, then remove the seal guide from the cylinder head cover.
5. Install a new spark plug to the no. 4 cylinder, then install all 4 ignition coils. (Click HERE)
6. Install the cylinder head cover bolts, and any remaining parts in the reverse order of removal. (Click HERE)
7. Perform all clear DTCs.
REPAIR PROCEDURE B
Cylinder Head Replacement with New Cylinder Head Cover
CAUTION
Please carefully read "Precaution for Handling Sodium-Filled Valves" and follow the instructions as the
exhaust valves contain metal sodium.
NOTE: Before starting this repair, make sure the spark plug tube was photographed with corrosion measurement
exceeding 12 mm.
1. Follow the procedure to remove and install the cylinder head. (Click HERE)
Page 6 of 6
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TSB/Document ID: A25-062
Replacement Service Bulletin Number:
MFR Communication Date: 2025-08-19
MFR Internal Campaign ID/Software Version:
Communication Type: Service Bulletin/Repair Instructions
NHTSA Components: ENGINE
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