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.
DTC B2739, Key-In-Ignition Fault: Notes
When ignition key is inserted fully in ignition switch, BCM receives a ground input through circuit No. 80 (Light Green wire) from ignition key alarm switch. DTC B2739 will set when BCM detects that IGN0 is active (when ignition switch is turned out of OFF position) and a ground signal is not received through circuit No. 80 for more than 0.3 second. No driver warning message will be displayed.
If BCM receives a key-in-ignition signal (ground) when ignition switch is not in OFF position, a current DTC will change to a history DTC. If conditions for malfunction no longer exist, history DTC will clear after 100 consecutive ignition cycles. DTC B2723 will also clear when scan tool is used to clear codes.
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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.