This article covers the wide body Honda Accord when fault codes P0301, P0302, P0303 or P0304 are stored in the ECU causing the check engine light to come on.
This is a common fault and Honda has released a bulletin 13-081 where you can find information about this repair.
A class action law suit in the USA has resulted in owners of these cars in the USA getting warranties extended and reimbursement for these repairs. No such action is recorded in Australia.
First up this fault only effects a certain VIN range.
So what’s the fault?
The Honda V6 had a system that disabled cylinders under certain conditions. This system is called Variable Cylinder Management. Whilst this was happening the piston rings were able to move causing the engine oil to enter the combustion chamber and foul up the spark plugs. Many technicians are just replacing the spark plugs and sending the client on their merry way only to have them return a few months later with the same fault. If you have a recurring spark plug fouling problem and fault codes that match those listed above, you probably have this issue.
The service bulletin indicates that any of the four fault codes listed above are the piston rings need to be replaced in the effected cylinder, however once you’re in there we advise replacing the piston rings on all cylinders. Its kinda stupid to do all that work just to replace one set of rings on one cylinder.
Once rebuilt a software update from Honda is required to avoid this happening again. We suspect this update disabled the Variable Cylinder Management, however this is only speculation and can’t be proven.
The rebuild can happen with the engine in the car however it is a huge job which requires the timing belt to be removed, again we advise replacing it whilst you’re there, the cylinder heads to be removed, the sump to be removed and then the pistons take out of the vehicle.
Cost for this repair will be in the thousands as labour alone is about sixteen hours for our experienced Honda technicians however if this is a first time for your mechanic you could expect it to take a lot longer.
Prices can vary depending on genuine parts costs vs aftermarket parts costs but if you are out of warranty and need this fault repaired we would estimate you wouldn’t get much change from $3500.
Be careful if looking to buy one of these secondhand or from a used car yard, you may be buying one that has had a new set of spark plugs and sent for a trade in.