AutoCodes – Cadillac – P0304 Cadillac

P0304 Cadillac Code - Cylinder 4 Misfire Detected

Quick Answer

A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. Common causes include Faulty Spark Plug #4, Clogged or faulty Fuel Injector #4, Faulty Ignition Coil #4. 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: P0304 Cadillac indicates Cylinder 4 Misfire Detected.
Common causes: Common causes include Faulty Spark Plug #4, Clogged or faulty Fuel Injector #4, Faulty Ignition Coil #4.
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 32,682

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 P0304 Cadillac 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 P0304 Cadillac - Cylinder 4 Misfire Detected - AutoCodes.com — P0304 Cadillac Code - Cylinder 4 Misfire Detected

What does this mean?

What are the Possible Causes of the DTC P0304 Cadillac?

Faulty Spark Plug #4
Clogged or faulty Fuel Injector #4
Faulty Ignition Coil #4
Fuel Injector #4 harness is open or shorted
Fuel Injector #4 circuit poor electrical connection
Ignition Coil #4 harness is open or shorted
Ignition Coil #4 circuit poor electrical connection
Insufficient cylinder 4 compression
Incorrect fuel pressure
Intake air leak

How to Fix the DTC P0304 Cadillac?

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 P0304 code means that cylinder 4 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 4. If the problem persists more tests need to be done to diagnose the problem, see "Possible Causes".

There is a Factory Service Bulletins for All 2000-2020 Cadillac Models:
2000-2020 Cadillac Factory Service Bulletin OBDII Code P0304
This Factory Service Bulletin explains how this condition may be caused by significant carbon build-up on the intake and/or exhaust valves due to fuel contamination or incomplete burning of the fuel.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0304 Cadillac 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 P0304 Cadillac Code

1. What does the OBDII code P0304 mean on a Cadillac?

P0304 indicates that the engine control module (ECM) has detected a misfire in cylinder 4 of your Cadillac.

2. What are the common symptoms of a P0304 code in a Cadillac?

Symptoms can include rough idling, reduced engine performance, poor fuel economy, hesitation during acceleration, and the check engine light turning on.

3. What causes a P0304 code on a Cadillac?

Common causes include a faulty spark plug, ignition coil, fuel injector issues, vacuum leaks, low compression in cylinder 4, or a problem with the ECM.

4. Can I drive my Cadillac with a P0304 code?

Driving with a P0304 code can cause further engine damage, including damage to the catalytic converter, so itâ€™s best to address the issue promptly.

5. How do I diagnose a P0304 code on a Cadillac?

Start by inspecting the spark plug, ignition coil, and fuel injector for cylinder 4. You may also need to perform a compression test or check for vacuum leaks.

6. How much does it cost to fix a P0304 code on a Cadillac?

The cost varies depending on the cause, ranging from $50 for a spark plug replacement to several hundred dollars for more complex repairs like fixing low compression.

7. Can a dirty fuel injector trigger a P0304 code?

Yes, a clogged or dirty fuel injector can cause insufficient fuel delivery to cylinder 4, leading to a misfire and triggering the P0304 code.

8. Will replacing the spark plug for cylinder 4 fix the P0304 code?

If the spark plug is the root cause of the issue, replacing it may resolve the problem. However, other components should also be inspected to rule out additional causes.

9. Could a vacuum leak cause a P0304 code in a Cadillac?

Yes, a vacuum leak near cylinder 4 can disrupt the air-fuel mixture, resulting in a misfire and triggering the code.

10. How can I prevent a P0304 code from occurring again?

Regular maintenance, including timely replacement of spark plugs, ignition coils, and fuel filters, as well as using high-quality fuel, can help prevent a recurrence of the P0304 code.