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.
Malfunction Indicator Lamp (MIL)
[EOBD]
A malfunction indicator lamp illuminates to notify the driver that there is a problem with the vehicle. However, the MIL will go off automatically after 3 subsequent sequential driving cycles without the same malfunction. Immediately after the ignition switch is turned on (ON position - do not start), the MIL will illuminate continuously to indicate that the MIL operates normally.
Faults with the following items will illuminate the MIL.
- Catalyst
- Fuel system
- Air Flow Sensor
- Intake Air Temperature Sensor
- Engine Coolant Temperature Sensor
- Throttle Position Sensor
- Heated Oxygen Sensor (Upstream)
- Heated Oxygen Sensor Heater (Upstream)
- Heated Oxygen Sensor (Downstream)
- Heated Oxygen Sensor Heater (Downstream)
- Injector
- Misfire
- Crankshaft Position Sensor
- Camshaft Position Sensor
- Evaporative Emission Control System
- Vehicle Speed Sensor
- Idle Speed Control System
- Power Supply
- ECM/PCM
- MT/AT Encoding
- Acceleration Sensor
- MIL-ON Request Signal
- Power Stage
- Refer to "Inspection Chart For Diagnostic Trouble Codes (DTC)" for more information.
[NON-EOBD]
A malfunction indicator lamp illuminates to notify the driver that there is a problem with the vehicle. However, the MIL will go off automatically after 3 subsequent sequential driving cycles without the same malfunction. Immediately after the ignition switch is turned on (ON position - do not start), the MIL will illuminate continuously to indicate that the MIL operates normally.
Faults with the following items will illuminate the MIL
- Heated oxygen sensor (HO2S)
- Mass Air Flow sensor (MAFS)
- Throttle position sensor (TPS)
- Engine coolant temperature sensor (ECTS)
- Idle speed control actuator (ISCA)
- Injectors
- ECM
- Refer to "Inspection Chart For Diagnostic Trouble Codes (DTC)" for more information.
[Inspection]
- After turning ON the ignition key, ensure that the light illuminates for about 5 seconds and then goes out.
- If the light does not illuminate, check for an open circuit in the harness, a blown fuse or a blown bulb.
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.