AutoCodes – Lexus – P0308 Lexus

P0308 Lexus Code - Cylinder 8 Misfire Detected

Quick Answer

When the engine misfires, high concentrations of Hydrocarbons (HC) enter the exhaust gas. Common causes include Intake air leak, Faulty spark plug #8, Faulty ignition coil #8. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0308 Lexus indicates Cylinder 8 Misfire Detected.
Common causes: Common causes include Intake air leak, Faulty spark plug #8, Faulty ignition coil #8.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 13,254

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Aug 25, 2022

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0308 Lexus Description

When the engine misfires, high concentrations of Hydrocarbons (HC) enter the exhaust gas. Extremely high hydrocarbon concentration levels can cause an increase in exhaust emission levels. Extremely high concentrations of hydrocarbons can also cause increases in the three-way catalytic converter temperature, which may cause damage to the three-way catalytic converter. To prevent this increase in emissions and to limit the possibility of thermal damage, the Engine Control Module (ECM) monitors the misfire count. When the temperature of the three-way catalytic converter reaches the point of thermal degradation, the ECM blinks the MIL. To monitor misfires, the ECM uses both the camshaft position sensor and the crankshaft position sensor. The camshaft position sensor is used to identify any misfiring cylinders and the crankshaft position sensor is used to measure variations in the crankshaft rotation speed. Misfires are counted when the crankshaft rotation speed variations exceed predetermined thresholds. If the misfire count exceeds the threshold levels and could cause emission control system performance deterioration, the ECM illuminates the MIL and stores a Diagnostic Trouble Code (DTC).

OBDII Code P0308 Lexus - Cylinder 8 Misfire Detected - AutoCodes.com — P0308 Lexus Code - Cylinder 8 Misfire Detected

What does this mean?

What are the Possible Causes of the DTC P0308 Lexus?

Intake air leak
Faulty spark plug #8
Faulty ignition coil #8
Clogged or faulty fuel injector #8
Fuel injectors #8 harness is open or shorted
Fuel Injectors #8 circuit poor electrical connection
Ignition coils #8 harness is open or shorted
Ignition coils #8 circuit poor electrical connection
Incorrect Fuel pressure
Faulty Mass Air Flow (MAF) Sensor
Faulty Engine Control Module (ECM)
Faulty Engine Coolant Temperature (ECT) Sensor

How to Fix the DTC P0308 Lexus?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

The P0308 code means that cylinder #8 is misfiring or is randomly misfiring. Start by checking for intake leaks and if no leaks are found the next step is to replace the spark plugs on cylinder #8. If the problem persists more tests need to be done to diagnose the problem. See "Possible Causes" for the most common problems.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0308 Lexus code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0308 Lexus Code

1. What does the OBDII code P0308 mean on a Lexus?

P0308 indicates a misfire has been detected in cylinder 8 of the engine.

2. What are the common symptoms of a P0308 code on a Lexus?

Symptoms include a rough idle, reduced engine performance, poor fuel economy, and occasionally the Check Engine Light flashing.

3. What causes a P0308 code on a Lexus?

Common causes include a faulty spark plug, ignition coil, a clogged fuel injector, low cylinder compression, or issues with the fuel delivery system.

4. Can a P0308 code damage my Lexus engine?

Yes, if left unresolved, it can cause severe engine damage, including overheating the catalytic converter or internal engine wear.

5. How do I diagnose a P0308 code on my Lexus?

Start by inspecting the spark plug, ignition coil, and cylinder 8 fuel injector. Perform a compression test if necessary to check for internal damage.

6. How can I fix a P0308 code on my Lexus?

Repairs may involve replacing the spark plug, ignition coil, or fuel injector for cylinder 8. In some cases, addressing fuel pressure issues or repairing internal engine components may be required.

7. Can a dirty air filter cause a P0308 code on a Lexus?

While unlikely, restricted airflow from a dirty air filter can contribute to misfires if it impacts overall engine performance.

8. Is it safe to drive with a P0308 code on my Lexus?

Driving with a P0308 code is not recommended, as it can lead to further engine damage or reduced drivability.

9. How much does it cost to fix a P0308 code on a Lexus?

The cost depends on the root cause. Replacing a spark plug or ignition coil might cost $100â€“$300, while addressing more severe issues like internal engine repairs could cost significantly more.

10. Can a vacuum leak cause a P0308 code on a Lexus?

Yes, a vacuum leak near cylinder 8 can lead to a lean air-fuel mixture and contribute to a misfire.