Auto Diagnostics

Hartford, WI | Erin, WI

Accurate Auto Diagnostics That Find Your Vehicle's Problems Fast

When your check engine light comes on or something feels off with your car, you need reliable answers quickly. At M&J Auto Sales & Service, we use advanced diagnostic equipment to identify what's actually happening under the hood. Our ASE certified technicians have over 75 years of combined experience reading computer codes, testing systems, and finding the source of automotive problems.

• Check engine light diagnostics
• Electrical system testing
• Engine performance analysis
• Transmission diagnostics
• ABS and airbag system checks
• Computer code reading and interpretation
• Sensor testing and verification
• Starting and charging system diagnostics

Reach out to us and we'll schedule your diagnostic appointment right away.

Modern Vehicles Need Professional Diagnostic Services

Cars today are loaded with computers and sensors, and those warning lights aren't something to ignore. When you're dealing with decreased fuel economy, strange noises, or dashboard warnings that won't go away, proper diagnostics save you time and money in the long run.

• Prevents guesswork and unnecessary repairs
• Identifies problems before they become expensive
• Clears confusing warning lights properly
• Provides accurate repair estimates
• Ensures your vehicle runs safely

Skip the trial-and-error fixes. Let our diagnostic tools and experienced technicians tell you exactly what needs attention.

Why Choose M&J Auto Sales & Service

As a locally owned, family owned shop in business since 2009, we've built our reputation on honest diagnostics and quality service. We're proud 2025 Car Fax Top 3 Service Center Award recipients and members of the Hartford, WI Chamber of Commerce.

• ASE certified technicians you can trust
• State-of-the-art diagnostic equipment
• 12-month/24,000-mile warranty on parts and labor
• Over 75 years of combined experience
• Works with all insurance and aftermarket warranty companies
• Transparent communication about what we find

We treat you how you'd like to be treated. That means no upselling and no surprise charges. Just straightforward diagnostics that help you make informed decisions about your vehicle.

Contact Us

Your vehicle's trying to tell you something, and we can help you understand what it needs. From Hartford to Erin and surrounding communities, our team is ready to provide the diagnostic services that give you peace of mind. We'll explain everything in plain language and present your options clearly.

Contact us today to schedule your auto diagnostics appointment and get the answers you need.