PRNDL Reverse Input Circuit Failure
The transmission control module can't detect when you shift into Reverse, like a light switch that won't register when flipped. This is usually a wiring or sensor connection problem in the gear selector circuit.
The ECU monitors the PRNDL (Park-Reverse-Neutral-Drive-Low) input signal from the transmission range sensor or gear selector switch. When you shift to Reverse, the sensor should send a specific voltage signal to confirm the gear position. If this signal is absent, shorted, or out of range, a circuit failure is detected.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Reverse Signal Voltage | 4.5-5.5V (typical logic high) | 0V, open circuit, or erratic signal |
| Signal Continuity | Complete circuit with <5 ohms resistance | Open circuit, >10 ohms, or intermittent connection |
Code B1627 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, B1627 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.