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.
Vehicle Security Module
The vehicle security module is on the ISO 9141 network. The vehicle security module controls the remote keyless entry (RKE) function as well as the power door locks. The ISO communication network will not function if the wire is shorted to ground or battery voltage. Check the network circuit between the vehicle security module C203b and the DLC C251. Total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the ISO network, damage to the DLC C251, damage to the vehicle security module C203b, or a problem in the in-line connector. For additional information, refer to MULTIFUNCTION ELECTRONIC MODULE .
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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.