Code Definition

B1578 — Lamp Park Input Circuit Short To Ground

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

About B1578

B1578 is a manufacturer-specific body diagnostic trouble code recorded for Ford vehicles. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B1578 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.

B1578 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 B1578 fault code is set by the Body Control Module (BCM) when it detects a short to ground on the lamp park input circuit. The park lamp input is a switched signal wire from the headlight switch that the BCM normally sees pulled high through an internal pull up when the switch is in OFF, and pulled to a defined low or active level when the operator selects park lamps. When the BCM sees the input held continuously at chassis ground at a time it should be at an inactive level, or sees an unexpectedly low source impedance to ground, it stores B1578. Symptoms can include parking lamps that fai...

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