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 B1440: Power Mode Master Input Circuit Mismatch: Description
Body Control Module (BCM) monitors Ignition 0, Ignition 1 and accessory signals from ignition switch. BCM uses voltage state (battery voltage or 0) and sequence of state changes to determine power mode called for by ignition switch. DTC B1440 is set when one of ignition switch circuits is shorted to either battery voltage or ground. Sequence of change of circuit is incorrect for expected power mode.
When DTC B1440 is set, BCM stores DTC B1440 to memory. BCM operates in a fail-safe power mode dependent on last valid power mode detected and state of engine run flag data on class 2 serial data communications circuits. Other modules on vehicle operate in a fail safe power mode dependent on last valid power mode transmitted by BCM and state of engine run flag on class 2 serial data communications circuits.
Current DTC B1440 will clear and become a history DTC when BCM detects a sequence of ignition switch inputs that match expected power mode. History DTC will clear after 100 ignition cycles with no repeated malfunction.
NO RELATED
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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.