Skip the auto shop - Our mechanics make house calls

Q: Getting code P0303

asked by on

I am getting a code P0303, which is for a cylinder 3 misfire. I am not sure, but I may need a coil replaced.

A: If you have already taken the first step of...

If you have already taken the first step of getting your codes scanned, the next thing to do would be to have an ignition test performed by a qualified technician. Attempting to do this yourself could result in being shocked by high voltage. This test would entail removing the ignition coil and placing the ignition tester in the circuit between the coil and the spark plug. If the spark plug or coil is faulty, the light will not flash consistently or at all on the ignition tester leading the technician to believe that either the coil or the plug is faulty for cylinder three. After confirming the lack of spark to cylinder three, the technician may erase your fault codes and switch your number three coil to the cylinder adjacent to it. When your Check Engine Light comes back on, if the misfire has switched to the other cylinder, the coil is faulty. If the misfire stays on cylinder three, the spark plug is faulty. If the spark plug is faulty, it is a good idea to have all spark plugs replaced at once.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: New battery car won't start

What you are describing sounds like a faulty starter solenoid. If you hear a clicking sound when turning the key, it is likely that your starter solenoid may be faulty. The starter solenoid is located on the starter and has...

Q: My cranks but won't start

If it is the security system then the dash security light will be on or flashing. If it was a sensor, then the Check Engine Light will be on and the engine computer will have set a code. You should...

Q: Leaking antifreeze from underneath the car.

Hi there. Check all of the cooling hoses on the engine, to the heater core, and to the radiator. See if any hoses are cracked. Check to see if the clamps are loose and need tightened or replaced. Look around...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...