Power Supply Sensor Circuit Short To Ground
A sensor that monitors the vehicle's power supply has a wire touching ground when it shouldn't, like a short circuit in an electrical cord. The ECU detected this abnormal connection and flagged it as a fault.
The ECU monitors the power supply sensor's voltage signal, expecting it to stay within a normal operating range. When the sensor circuit shorts to ground, the voltage drops to zero or near-zero, triggering a fault code. The ECU uses this voltage reading to verify proper power distribution and system health.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Sensor Voltage | 4.5-5.5V or system-specific supply voltage | Below 0.5V or shorted to ground |
| Circuit Resistance | Open circuit or high resistance | Low resistance path to ground |
Code B1299 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.
Once the fault is repaired, B1299 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.