Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
The car's computer noticed that cylinder number 9 in the engine isn't working properly. It's like when one of the pistons in a row of bicycle pedals doesn't push, making the ride bumpy.
A misfire occurs when the air-fuel mixture in a cylinder does not ignite properly. This can cause the engine to run rough and may lead to increased emissions.
The P0309 code indicates that the powertrain control module (PCM) has detected a misfire in cylinder 9. This can be due to a variety of issues such as a faulty spark plug, ignition coil, or fuel injector. The PCM monitors the crankshaft position sensor and detects variations in the crankshaft speed which indicate a misfire.
• Check Engine Light is on
• Rough engine idle
• Poor acceleration
• Increased fuel consumption
• Faulty spark plug in cylinder 9
• Defective ignition coil
• Clogged or faulty fuel injector
• Vacuum leak
• Low fuel pressure
PCM: Powertrain Control Module
OBD-II: On-Board Diagnostics II
• Use an OBD-II scanner to confirm the code P0309.
• Inspect the spark plug and ignition coil for cylinder 9.
• Check the fuel injector for cylinder 9.
• Perform a compression test on cylinder 9.
• Replace the spark plug for cylinder 9.
• Replace the ignition coil for cylinder 9.
• Clean or replace the fuel injector for cylinder 9.
• Repair any vacuum leaks.
• OBD-II scanner
• Spark plug socket
• Multimeter
• Compression tester
$150 - $400
Moderate
• Ford F-150
• Chevrolet Silverado
• Dodge Ram
• Regularly replace spark plugs and ignition components.
• Use high-quality fuel.
• Perform regular engine maintenance.
Engine Performance
• Do not ignore the Check Engine Light.
• Have the vehicle inspected by a professional if unsure.
• Avoid driving the vehicle hard until the issue is resolved.
Check with your vehicle manufacturer for powertrain warranty coverage.
Misfire codes are common in vehicles with high mileage or poor maintenance history.
Moderate – It is recommended to address this issue soon to prevent further engine damage.
Ignoring this code can lead to increased emissions and potential engine damage.
• Engine must be running.
• Vehicle should be at operating temperature.
Cylinder 9 is located on the engine block, typically on the right bank of a V8 or V10 engine.
Q: Can I drive with a P0309 code?
A: It's possible to drive short distances, but it's not recommended as it can cause further engine damage.
Q: How can I reset the P0309 code?
A: You can reset the code using an OBD-II scanner, but it's important to fix the underlying issue first.
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Fitment Required · Vehicle-fitment part
Commonly relevant for misfire, ignition-efficiency, and some drivability-related repairs.
Misfire and ignition-related faults commonly involve spark plugs as part of the repair path.
Check the correct plug type, gap, and engine application for your vehicle.
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Fitment Required · Vehicle-fitment part
Relevant when the fault points toward ignition-coil performance or cylinder-specific ignition issues.
Some ignition faults involve coil performance or cylinder-specific coil problems.
Match the coil to your engine and confirm the failed component before ordering.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.