P0305: Cylinder 5 Misfire Detected

written by Edmunds.com^{This story was created with generative AI and was reviewed and fact-checked by our staff of editors and experts.}
edited by Brett T. Evans^{Correspondent
Brett T. Evans has been an auto writer for more than a decade with 2,000 articles under his belt, covering topics as varied as tuned diesel trucks, modern supercars and experimental electric vehicles. Brett contributes to Edmunds and has also written for Petrolicious, MotorTrend, Out Motorsports and Motor1, among others. When he's away from his desk, Brett enjoys off-roading in his 1996 Lexus LX 450 or cutting up a twisty road in his 2006 BMW Z4 3.0si — sometimes with a border collie named Lilly in tow.}
12/13/2024
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What does the P0305 error code mean?

The P0305 diagnostic trouble code indicates a "Cylinder 5 Misfire Detected." This code appears when the engine control module identifies inconsistent combustion in the fifth cylinder. Misfires occur when the air-fuel mixture in the cylinder fails to ignite properly, leading to rough engine performance and reduced efficiency.

The importance of addressing P0305

A misfire in cylinder 5 can significantly impact engine performance, fuel economy and emissions. Left unaddressed, this issue may cause additional damage to the engine, such as catalytic converter failure or increased wear on other components. Timely resolution is crucial to prevent expensive repairs and ensure optimal vehicle operation.

A cylinder misfire can also indicate a larger problem with the car’s engine. Figuring out the original cause of the misfire and repairing it can prevent further issues.

Can I safely drive my car with this error code?

Driving with the P0305 code is not recommended. While the vehicle might still run, a misfire can cause the engine to operate inefficiently, leading to vibrations, reduced power, and potentially unsafe conditions during driving. Prolonged use in this state may also result in severe engine damage or catalytic converter failure.

Common symptoms of P0305

Illuminated check engine light
Rough idling or engine vibrations, especially under throttle
Reduced power and acceleration
Poor fuel economy
Noticeable hesitation during throttle input
Possible fuel odor from the exhaust

Diagnosing P0305

Diagnosing the P0305 code involves several key steps:

Scan for codes: Use an OBD-II scanner to confirm the P0305 code and check for any related codes.
Inspect spark components: Examine the spark plug, ignition coil and wiring on cylinder 5 for signs of wear or damage.
Check fuel delivery: Verify that the fuel injector for cylinder 5 is functioning correctly and not clogged.
Perform a compression test: Ensure cylinder 5 has adequate compression to support proper combustion.
Inspect for vacuum leaks: Check for leaks near cylinder 5 that could disrupt the air-fuel mixture.
Analyze live data: Use a scanner to observe real-time engine parameters, such as misfire counters and fuel trim.

Repairing P0305

Repairing the P0305 code typically involves:

Replacing a faulty spark plug or ignition coil for cylinder 5.
Repairing or replacing damaged wiring or connectors.
Cleaning or replacing a clogged or malfunctioning fuel injector.
Resolving vacuum leaks or addressing intake manifold issues near cylinder 5.
Addressing internal engine issues, such as a valve problem or low compression, if necessary.
Clearing the code and performing a test drive to confirm the repair’s effectiveness.

Getting other error codes?

Visit Edmunds' catalog of ODB-II diagnostic trouble codes to help assess your vehicle's issue.

by Edmunds.com

This story was created with generative AI and was reviewed and fact-checked by our staff of editors and experts.

edited by Brett T. Evans

Brett T. Evans has been an auto writer for more than a decade with 2,000 articles under his belt, covering topics as varied as tuned diesel trucks, modern supercars and experimental electric vehicles. Brett contributes to Edmunds and has also written for Petrolicious, MotorTrend, Out Motorsports and Motor1, among others. When he's away from his desk, Brett enjoys off-roading in his 1996 Lexus LX 450 or cutting up a twisty road in his 2006 BMW Z4 3.0si — sometimes with a border collie named Lilly in tow.