What is OBD-II and does my car support it?

OBD-II (On-Board Diagnostics II) is a standardized system in all cars manufactured after 1996 in the US and 2001 in the EU. If your car was built after these dates, it almost certainly has an OBD-II port, typically located under the dashboard near the steering column.

How does GaugeAI diagnose car problems?

GaugeAI uses advanced AI models trained on millions of diagnostic records to analyze your OBD-II error codes, sensor data, and vehicle information. It cross-references manufacturer-specific databases to provide accurate, plain-English explanations and repair recommendations.

What OBD-II scanners are compatible with GaugeAI?

GaugeAI works with any ELM327-based Bluetooth or WiFi OBD-II scanner. Popular options include BAFX Products, Veepeak, and BlueDriver. You can also upload data manually through photos, CSV files, or raw diagnostic logs.

Is GaugeAI accurate enough to replace a mechanic?

GaugeAI achieves 99.2% accuracy in code interpretation and provides detailed repair guidance. While it is an excellent first-line diagnostic tool that can save unnecessary mechanic visits, we recommend professional inspection for complex repairs and safety-critical issues.

Which car brands and models does GaugeAI support?

GaugeAI supports over 10,000 vehicle models across all major manufacturers including Toyota, Honda, BMW, Mercedes-Benz, Ford, Chevrolet, Hyundai, Kia, Volkswagen, Nissan, Changan, and many more. Our AI is trained on manufacturer-specific diagnostic data for more precise results.

How much does GaugeAI cost?

GaugeAI offers a free plan with 5 diagnostic scans per month. Our Pro plan at $14/month includes unlimited scans, full diagnostic history, repair cost estimates, and priority AI analysis. Fleet plans start at $89/month for businesses managing multiple vehicles.

Is my vehicle data secure and private?

Absolutely. All diagnostic data is encrypted in transit and at rest using AES-256 encryption. We never share your vehicle data with third parties. You can delete your data at any time from your account settings. We are SOC 2 Type II compliant.

Can I use GaugeAI without an OBD-II scanner?

Yes. While direct OBD-II connection gives the most comprehensive results, you can also upload photos of your dashboard warning lights, paste error codes manually, upload CSV data exports from other tools, or share scanner screenshots for AI analysis.

High SeverityDo Not Drive

What does P0304 mean?

Cylinder 4 Misfire Detected

Direct Answer

P0304 indicates a misfire in cylinder 4. On 4-cylinder engines, cylinder 4 is typically at the opposite end of the engine from cylinder 1. The coil-swap diagnostic method is the fastest way to isolate the cause.

Common Symptoms

✓Check engine light on
✓Rough idle
✓Poor power
✓Engine vibration

Common Causes

01Worn or fouled spark plug
02Faulty coil on cylinder 4
03Failed injector
04Low cylinder compression

How to Fix P0304

Coil swap test

Swap cylinder 4 coil with cylinder 2. If misfire moves to P0302, replace the coil.

Replace spark plug

Check for wear, oil fouling, or carbon buildup.

Injector test

Noid light test confirms injector signal. Injector cleaner or professional cleaning for partially clogged units.

Frequently Asked Questions

Can a bad catalytic converter cause P0304?

No — it's the reverse. P0304 (misfire) causes catalytic converter damage, not the other way around. A bad catalytic converter can cause back-pressure issues that affect performance but does not directly cause cylinder-specific misfires.

Estimated Repair Cost

$30–$1500

Spark plug: $10–$50. Coil: $50–$200. Injector: $150–$400.

Safe to Drive?

No — avoid driving

Stop if light is flashing. Limit driving otherwise.

Related Codes

P0300 P0301 P0302 P0303

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