Code Definition

B1813 — Lamp Backup Switch Input Circuit Short To Ground

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

About B1813

B1813 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 B1813 is stored, the module has detected a short-circuit (voltage pulled to ground or to supply) 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.

B1813 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 on the transmission to determine when reverse has been selected. DTC B1813 sets when the BCM detects that the backup switch input line is being pulled to chassis ground at a time when the switch should be open and the input should sit at the inactive reference state, indicating that the wiring or the switch itself has shorted to ground somewhere between the switch contacts and the BCM input pin. On platforms where the switch closes to ground in the active state, a hard short to ground produces a permanently acti...

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