Driver Power Window One Touch Window Relay Circuit Open
The circuit controlling the driver's one-touch power window relay is broken or disconnected, like a light switch with a severed wire. The window motor won't respond to the one-touch automatic function even though manual operation might still work.
The BCM monitors voltage and current flow through the one-touch window relay circuit. It expects to detect proper voltage when the relay is commanded on and verifies circuit continuity. An open circuit prevents current flow, triggering the fault.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Relay Circuit Voltage | 12V when activated, 0V when de-activated | No voltage detected or incomplete circuit continuity |
| Circuit Continuity | <5 ohms resistance | >50 ohms or open circuit |
Code B1399 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, B1399 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.