Diagnostic reference
System Diagnostics
Engine, fuel, ignition, electrical, starting, charging and network diagnosis. Choose a system, understand the evidence, then follow the related test procedure.
Engine Performance
Misfire Diagnosis
Diagnose ignition, fuel, mechanical, and control-related misfires
Read guide →Fuel Trim Analysis
Use short-term and long-term fuel trim to diagnose mixture problems
Read guide →Airflow Diagnosis
Evaluate MAF, MAP, throttle, and engine airflow data
Read guide →Engine Timing
Diagnose valve timing and cam/crank correlation problems
Read guide →Compression
Evaluate cylinder sealing and mechanical engine condition
Read guide →Exhaust Restrictions
Diagnose restricted catalytic converters and exhaust systems
Read guide →Fuel System
Ignition System
Electrical
Voltage Drop Testing
Locate excessive resistance in automotive circuits
Read guide →Open Circuit Diagnosis
Locate breaks that prevent current flow
Read guide →Short Circuit Diagnosis
Diagnose shorts to ground and shorts to power
Read guide →Parasitic Draw
Diagnose excessive key-off battery current draw
Read guide →Starting & Charging
Network Diagnostics
CAN Bus Basics
Understand high-speed automotive CAN communication
Read guide →CAN Resistance Testing
Use resistance measurements as part of CAN diagnosis
Read guide →U-Code Diagnosis
Diagnose communication-related diagnostic trouble codes
Read guide →CAN Scope Testing
Evaluate CAN High and CAN Low with an oscilloscope
Read guide →