P0307 Code (Symptoms, Causes, and How to Fix)

Last Updated on March 10, 2023

Few things will ruin an otherwise peaceful commute quite like the sudden and unexpected illumination of your vehicle’s check engine light. Such circumstances often lead one to feel aggravated, if not completely bewildered, as the thought of costly repairs to come, run rampant.

More often than not, a motorist is also left wondering whether they are causing additional harm by continuing on their commute.

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In truth, a check engine light can mean a lot of things. All check engine lights are not one and the same, as the illumination of such a light simply means that a vehicle’s operating software has logged a diagnostic trouble code of one particular type or another.

These faults can ultimately be read with the use of an OBD-II scan tool, providing valuable clues that can be used during the diagnostic process.

The ability to read and analyze diagnostic trouble codes is especially helpful when attempting to troubleshoot misfire-related issues. In many cases, an active fault code will actually identify the specific cylinder on which the misfire is located. This is the case with diagnostic trouble code P0307, which relates to a cylinder #7 misfire event.

Read on to learn more about diagnostic fault code P0307, as well as how to address such issues, should they arise in the future.

What Does Code P0307 Mean?

OBD-II Trouble Code P0307 Description
Misfire Detected in #7 Cylinder

Diagnostic fault code P0307 relates to a recorded misfire event, isolated to an engine’s #7 cylinders. Simply put, a vehicle’s ECM/PCM has determined that the engine’s number #7 cylinder has failed to produce adequate combustion on one or more occasions, thereby presenting a cylinder-to-cylinder imbalance. As such, the engine’s #7 cylinder is not contributing as it otherwise should.

Under most circumstances, a P0307 diagnostic fault code is triggered whenever the number of crankshaft revolutions per minute has deviated in either direction by more than 2 percent.

Data gathered from an engine’s camshaft position sensor is then used to isolate the offending cylinder. Nonetheless, further diagnosis will be required to determine the underlying cause of this misfire.

Related: P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0308

Symptoms of Code P0307

car not starting

Diagnostic fault code P0307 is often accompanied by a host of secondary symptoms, some of which tend to be more pronounced than others. Learning to recognize these individual symptoms can prove helpful when attempting to diagnose the issue at hand.

The following are several of the most common symptoms associated with diagnostic fault code P0307.

Causes of Code P0307

Diagnostic fault code P0307 can be caused by a host of individual underlying issues, a number of which can be somewhat tricky to isolate and diagnose. Familiarizing yourself with these potential causes can pay dividends when trying to remedy the issue in question.

The following are several of the most common causes of diagnostic fault code P0307.

Is Code P0307 Serious?

Diagnostic fault code P0307 is generally considered to be of moderate severity, as it indicates that an engine is producing little to no power on its #7 cylinder. Therefore, the affected engine is unable to meet typical power demands as it otherwise would. Additionally, some of the symptoms associated with DTC P0307 can prove detrimental to a vehicle’s driveability.

It is also worth noting that depending upon the root cause of an engine’s misfire, a condition of this nature, if left untreated, can actually lead to catalyst damage with time.

A lack of spark ignition on a specific cylinder leads to the downrange dosage of raw fuel into a vehicle’s exhaust. This fuel is prone to cause superheating within the exhaust system’s catalytic convertor.

In any event, the root cause of a vehicle’s P0307 fault code should be thoroughly diagnosed and repaired as soon as possible. Doing so can promptly restore overall engine performance, while also mitigating the risk of further damage.

If you do not feel comfortable tackling such repairs yourself, an appointment should be made with a trusted service center at the first available opportunity.

How to Fix Code P0307

how to check spark plugs

The following steps can be followed to assist in diagnosing and repairing the root cause of a vehicle’s P0307 fault code. As always, one should always consult a factory-specific service manual for their particular vehicle, before tackling any such repairs.

#1 – Check For Additional DTCs

Before beginning the diagnostic process, check for the presence of additional fault codes. Any such faults should be thoroughly diagnosed and repaired before proceeding.

#2 – Inspect/Test Ignition System Components

Begin by closely inspecting your engine’s #7 plug wire/coil pack for visual signs of damage, or grounding. The spark plug for this cylinder should also be removed and inspected.

The inspection of an engine’s distributor cap and rotor button is also advised, where applicable. Replace all components that appear damaged or worn. In many cases, an inline spark tester can be used to verify power delivery to the affected plug.

#3 – Test Fuel Injector Function

With the use of a bi-directional scan tool, and a suitable pressure gauge tied into the engine’s fuel rail, check for pressure fluctuations when commanding the #7 injector to cycle.

If functioning properly, the observed pressure should dip momentarily. If this does not occur, further testing will be required to prove circuit viability.

#4 – Check Compression

With the engine warmed to operating temperature, compression should be checked on the #7 cylinder. Readings taken from this testing should be compared to specified values given by the vehicle’s manufacturer.

#5 – Analyze Freeze Frame Data

Next, you should analyze freeze frame data logged in relation to the P0307 fault that has been stored. Care should be taken to isolate any sensor-related values that appear irregular, or out of range.

Most notably, one should carefully analyze the O2 sensor, MAF sensor, camshaft sensor, and crankshaft sensor data.

Josh Boyd

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