Code Definition

B1811 — Lamp Backup Switch Input Circuit Open

System: Body  |  Type: Manufacturer-Specific  |  Make: Generic

About B1811

B1811 is a manufacturer-specific body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B1811 is stored, the module has detected an open (broken or disconnected) electrical path in the monitored circuit.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

B1811 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The Body Control Module (BCM) monitors an input signal from the backup lamp switch, typically a mechanical switch on the transmission housing or an internal contact within the transmission range sensor, that closes when the gear selector is moved into reverse. DTC B1811 sets when the BCM detects an open circuit specifically on the backup switch input, meaning the input remains at the inactive reference state regardless of gear selector position. The BCM may detect this by comparing the input state against the transmission range sensor, by failing to see the expected change in voltage when reve...

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