AutoCodes – Pontiac – P0305 Pontiac

P0305 Pontiac Code - Cylinder 5 Misfire Detected

Quick Answer

A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. Common causes include Faulty spark plug 5, Clogged or faulty fuel injector 5, Faulty ignition coil 5. 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: P0305 Pontiac indicates Cylinder 5 Misfire Detected.
Common causes: Common causes include Faulty spark plug 5, Clogged or faulty fuel injector 5, Faulty ignition coil 5.
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 14,634

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 09, 2022

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0305 Pontiac Description

A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. The Engine Control Module (ECM) can detect these variations by closely monitoring the crankshaft position sensor signal. The signals of the camshaft position sensors are used to determine which cylinder is misfiring. If the ECM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, the Diagnostic Trouble Code (DTC) will be set. Under certain driving conditions, a misfire rate can be high enough to cause the catalytic converter to overheat, damaging the converter. The Malfunction Indicator Lamp (MIL) flashes when the converter is overheating, damaging conditions are present, and the DTC is set. The DTC will be set when the ECM detects a crankshaft rotation speed variation indicating a single-cylinder misfire rate sufficient to cause emissions levels to exceed mandated standards.

OBDII Code P0305 Pontiac - Cylinder 5 Misfire Detected - AutoCodes.com — P0305 Pontiac Code - Cylinder 5 Misfire Detected

What does this mean?

What are the Possible Causes of the DTC P0305 Pontiac?

Faulty spark plug 5
Clogged or faulty fuel injector 5
Faulty ignition coil 5
Fuel injector 5 harness is open or shorted
Fuel injector 5 circuit poor electrical connection
Ignition coil 5 harness is open or shorted
Ignition coil 5 circuit poor electrical connection
Insufficient cylinder 5 compression
Incorrect fuel pressure
Intake air leak

How to Fix the DTC P0305 Pontiac?

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 P0305 code means that the cylinder 5 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 5. If the problem persists more tests need to be done to diagnose the problem, see "Possible Causes".

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0305 Pontiac 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 P0305 Pontiac Code

1. What does the OBDII code P0305 mean on a Pontiac?

P0305 indicates that the engine control module (ECM) has detected a misfire in cylinder 5 of your Pontiac’s engine.

2. What are the symptoms of a P0305 code in a Pontiac?

Symptoms may include rough idling, engine hesitation, reduced power, poor fuel economy, and the check engine light turning on.

3. What are the common causes of a P0305 code in a Pontiac?

Common causes include a faulty spark plug, a defective ignition coil, a clogged fuel injector, low cylinder compression, or a vacuum leak near cylinder 5.

4. Can a P0305 code damage my engine if ignored?

Yes, prolonged misfires can cause damage to the catalytic converter, increase emissions, and lead to more severe engine problems over time.

5. How do I diagnose a P0305 code in a Pontiac?

Start by inspecting the spark plug, ignition coil, and fuel injector for cylinder 5. A compression test or a vacuum leak check may also help pinpoint the issue.

6. Can a dirty fuel injector cause a P0305 code?

Yes, a clogged or malfunctioning fuel injector for cylinder 5 can cause improper fuel delivery, leading to a misfire.

7. How much does it cost to repair a P0305 code on a Pontiac?

The cost depends on the cause. Replacing a spark plug or ignition coil may cost $100-$300, while more extensive repairs like addressing low compression can cost significantly more.

8. Can I drive my Pontiac with a P0305 code?

Driving with a P0305 code is not recommended, as it can lead to poor performance, increased fuel consumption, and potential engine or catalytic converter damage.

9. Could a vacuum leak trigger a P0305 code?

Yes, a vacuum leak near cylinder 5 can cause an air-fuel imbalance, resulting in a misfire and triggering the P0305 code.

10. Do I need a professional mechanic to fix a P0305 code?

While some causes, like replacing a spark plug, are DIY-friendly, diagnosing and repairing issues like low compression or fuel injector failure may require a professional mechanic.