Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Mode II (Self-Diagnostics)
When Mode II is accessed (engine not running), codes stored in ECU memory will be flashed by CHECK ENGINE light (if equipped) and red LED on side of ECU.
A long flash (.6 second) indicates first digit of code. Short flashes (.3 second) indicates second digit of code. For example: 1 long flash followed by 2 short flashes indicate a Code 12. See Fig 1 .
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.