Power Window One Touch Up/Down Activated Simultaneously
Your car's power window system detected both the up and down buttons being pressed simultaneously, which shouldn't happen during normal operation. Think of it like trying to push a door open and closed at the same time—the system caught a conflicting command.
The body control module monitors the switch input voltage signals from the power window control switch. It detects when both up and down signals are active simultaneously, which indicates a short circuit, stuck switch, or wiring fault. The ECU expects only one command at a time under normal conditions.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Switch Signal State | Only one button active (up OR down) at any given time | Both up AND down signals detected simultaneously |
| Signal Voltage | Isolated high/low states per button | Conflicting voltage levels indicating cross-contact or short |
Code B1478 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, B1478 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.