CHECK ENGINE LIGHT DIAGNOSTIC & REPAIR

FREE DIAGNOSTIC SCAN(Save with our complimentary service)

Don't ignore that warning light! Get honest answers and fair pricing from Rohnert Park's most trusted auto repair shop.

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Is Your Check Engine Light Flashing?

A flashing check engine light indicates severe engine misfires that can destroy your catalytic converter in minutes. STOP DRIVING IMMEDIATELY and have your vehicle towed to prevent costly catalytic converter damage.

Why Choose Rohnert Park Transmission for Check Engine Light Repair?

When your check engine light comes on, you need answers - not sales pitches. At Rohnert Park Transmission, we've been providing honest diagnostics and fair repairs since 1989. While other shops use that warning light as an opportunity to sell unnecessary services, we focus on finding the real problem and fixing it right the first time.

Our Diagnostic Promise:

✓ FREE complete diagnostic scan
✓ Same-day diagnosis on most vehicles
✓ Written estimate before any repairs
✓ No pressure, no unnecessary upsells
✓ ASE Master Certified technicians
✓ 2-year/24,000-mile warranty on repairs

Common Check Engine Light Causes & Solutions

Your check engine light monitors over 100 different systems. Here are the most common issues we diagnose and repair:

Problem	Symptoms	Service Level	If Ignored
Oxygen Sensor Failure	Poor fuel economy, rough idle, failed emissions	Moderate repair	Expensive catalytic converter damage
Loose/Bad Gas Cap	Fuel smell, check engine light only	Minor service	Failed emissions test
Catalytic Converter	Reduced power, dark exhaust smoke, sulfur smell	Major repair	Complete engine failure
Mass Airflow Sensor	Stalling, hard starting, poor acceleration	Moderate repair	Engine damage, 25% MPG loss
Spark Plugs/Ignition Coils	Engine misfires, rough idle, poor acceleration	Variable repair	Catalytic converter damage
EVAP System Leak	Fuel smell, difficulty filling tank	Moderate repair	Failed emissions, environmental fines

💡 Money-Saving Tip:

Many shops will replace parts without proper diagnosis. We've seen customers spend significant amounts on unnecessary repairs because their mechanic was "guessing." Our free diagnostic pinpoints the exact problem, preventing unnecessary repairs and expenses.

The Real Cost of Ignoring Your Check Engine Light

Damage Progression Timeline

Day 1:

Light comes on, minor issue detected

Week 1:

10-20% decrease in fuel economy begins

Month 1:

Related components start failing

Month 3:

Major damage occurs (catalytic converter, engine)

Month 6:

Complete system failure possible

Financial Impact

Lost fuel economy (3 months):Significant cost
Failed emissions test:Retest fees
Secondary damage:Major expense
Potential engine replacement:Extensive cost
Total potential cost:Thousands in repairs

Compare to average check engine light repair: Affordable service

Our Professional Diagnostic Process

We don't just read codes - we perform comprehensive diagnostics to find the root cause

OBD-II Computer Scan

We connect professional-grade diagnostic equipment to read all stored codes, pending codes, and freeze frame data. Unlike parts store code readers, our equipment shows live data streams and can perform active tests.

Time: 10-15 minutes

Visual & Physical Inspection

Our ASE-certified technicians inspect related components for visible damage, loose connections, or wear. Many check engine light issues are caused by simple problems like damaged vacuum hoses or corroded connectors.

Time: 15-20 minutes

Test Drive & Live Data Analysis

We perform a diagnostic test drive while monitoring live sensor data. This reveals intermittent problems and confirms whether components are operating within specifications under real driving conditions.

Time: 10-15 minutes

Component Testing

Using specialized tools, we test specific components identified in the diagnosis. This includes multimeter testing, pressure testing, and oscilloscope analysis to confirm the exact failure point.

Time: 20-30 minutes

Written Report & Estimate

You receive a detailed report showing all findings, required repairs, and exact costs. We explain everything in plain English and answer all your questions. No pressure, no surprises.

Time: 10 minutes

Same-Day Diagnosis Guarantee

For vehicles dropped off before 2 PM, we guarantee same-day diagnosis or your next oil change is free!

Why Rohnert Park Trusts Us

Honest, Transparent Service

✓Free diagnostics with no obligation
✓Written estimates before any work
✓We show you the failed parts
✓No unnecessary upsells or scare tactics
✓Second opinions welcomed

Professional Expertise

✓ASE Master Certified technicians
✓35+ years serving Sonoma County
✓Latest diagnostic equipment
✓Factory-level programming capability
✓2-year/24,000-mile warranty

Real Customer Story

"Another shop told me I needed an expensive catalytic converter replacement. Rohnert Park Transmission's free diagnostic found it was just a bad oxygen sensor. They provided an affordable repair and my car runs perfectly. They saved me from a major unnecessary expense!"

- Sarah M., Rohnert Park

Frequently Asked Questions

Is it safe to drive with the check engine light on?

If the light is solid, you can usually drive to a repair shop, but get it diagnosed soon to prevent further damage. If the light is flashing, stop driving immediately - this indicates severe engine misfires that can destroy your catalytic converter in minutes, resulting in costly repairs.

How much does a check engine light diagnostic cost?

At Rohnert Park Transmission, diagnostic scans are completely FREE. We provide complimentary diagnostics while others may charge for the same service. We believe in transparent, honest service - we'll tell you exactly what's wrong with competitive repair pricing and no obligation to proceed.

What are the most common check engine light causes?

The top causes are: 1) Oxygen sensor failure, 2) Loose gas cap, 3) Catalytic converter issues, 4) Mass airflow sensor problems, 5) Spark plugs or ignition coils, and 6) EVAP system leaks. Each repair varies in complexity and cost.

Will my car pass emissions testing with the check engine light on?

No, your vehicle will automatically fail California emissions testing if the check engine light is on. Even if you clear the codes, the vehicle's readiness monitors must complete their cycles before testing, which can take 50-100 miles of specific driving conditions.

Can AutoZone or O'Reilly fix my check engine light?

While parts stores offer free code reading, they cannot perform repairs or detailed diagnostics. Code readers only provide error codes, not the actual diagnosis. Our ASE-certified technicians use professional diagnostic equipment and perform comprehensive testing to identify the root cause, not just the symptom.

How long does check engine light diagnosis take?

Our complete diagnostic process typically takes 60-90 minutes. For vehicles dropped off before 2 PM, we guarantee same-day diagnosis. We'll call you with results and a detailed estimate before any repairs begin.

Can I clear the check engine light myself?

While you can clear codes with an OBD-II scanner, the light will return if the problem isn't fixed. Additionally, clearing codes resets your vehicle's readiness monitors, which means you'll fail emissions testing until the monitors complete (50-100 miles of driving). It's better to fix the actual problem.

What if I can't afford the repair right now?

We offer flexible financing options through our partnership programs. We can also prioritize repairs if multiple issues exist, fixing the most critical problems first. Our free diagnostic helps you make informed decisions about your vehicle's needs and budget.

Don't Let a Small Problem Become a Big Expense

Get your FREE check engine light diagnostic today and save hundreds or thousands in preventable repairs.

Same-Day Service Available!

Drop off before 2 PM for guaranteed same-day diagnosis

Call (707) 584-7727 Schedule Online

📍 6001 Commerce Blvd, Rohnert Park, CA 94928
⏰ Monday-Friday: 8:00 AM - 5:30 PM