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 communications network. The vehicle security module controls the remote keyless entry (RKE) function as well as the power door locks. The ISO 9141 communications network does not function if the circuit is shorted to ground or battery voltage. Check the communications network circuit 70 (LB/WH) between the vehicle security module C203b and the DLC C251. The 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 9141 communications 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 MODULES .
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.