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.
Check Engine Light
CHECK ENGINE or Malfunction Indicator Light (MIL) is illuminated when any of the following occur:
- Completion of the next consecutive driving cycle where the previously faulted system is monitored again and the emissions relevant fault is again present. See Fig 1.
- Immediately if a catalyst damaging fault occurs.
- A malfunction of a component that can affect the emission performance of the vehicle occurs and causes emissions to exceed 1.5 times the standard.
- Manufacturer-defined specifications are exceeded.
- An implausible input signal is generated.
- Catalyst deterioration causes HC-emissions to exceed a limit equivalent to 1.5 times the standard.
- Misfire faults occur.
- A leak is detected in the evaporative system.
- The oxygen sensors observe no purge flow from the purge valve/evaporative system.
- Engine control module fails to enter closed-loop operation within a specified time interval.
- Engine control or automatic transmission control enters a limp home operating mode.
- Key is in the ignition on position before cranking (Bulb Check Function).
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.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
No obligation. See pricing before you book.