How to Diagnose Car Problems
Learn how to diagnose car problems with our detailed step-by-step guide. Follow our easy instructions to get it done right.
Your Progress
0 of 6 steps completedStep-by-Step Instructions
1 Step 1: Identify Symptoms and When They Occur
Step 1: Identify Symptoms and When They Occur
Note specific symptoms, when problem happens (cold start, highway speed, etc.), and duration.
Automotive Diagnostic Guide
Reference book for troubleshooting common car problems
2 Step 2: Scan for Diagnostic Trouble Codes
Step 2: Scan for Diagnostic Trouble Codes
Use OBD2 scanner to pull any stored fault codes, research codes for potential causes.
OBD2 Scanner
Professional code reader with live data viewing
3 Step 3: Perform Visual Inspection
Step 3: Perform Visual Inspection
Check for obvious issues: leaks, worn belts, loose connections, damaged hoses, unusual wear.
LED Work Light
Bright rechargeable light for inspecting engine bay
4 Step 4: Test Related Systems
Step 4: Test Related Systems
Based on symptoms, test battery voltage, fuel pressure, compression, or other relevant systems.
Digital Multimeter
Voltage and resistance tester for electrical diagnosis
Fuel Pressure Tester
Gauge for testing fuel system pressure
5 Step 5: Research Problem and Narrow Down Cause
Step 5: Research Problem and Narrow Down Cause
Use online forums, repair databases, or service manuals to identify likely causes.
Repair Manual Subscription
Online access to factory service information
6 Step 6: Test Fix or Seek Professional Help
Step 6: Test Fix or Seek Professional Help
Replace suspected component and verify fix, or consult mechanic if diagnosis is unclear.