Code Definition

B1594 — Autolamp Delay Decrease Circuit Short To Ground

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

About B1594

B1594 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 B1594 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.

B1594 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) on Ford, Lincoln, and Mercury vehicles equipped with the Autolamp system monitors the autolamp delay decrease signal wire from the headlamp switch potentiometer, which is used by the driver to shorten the headlamp delay time after key off. DTC B1594 sets when the BCM detects that the autolamp delay decrease circuit is shorted to ground, meaning the input voltage is being pulled to zero or near zero outside its expected operating range. This is most commonly caused by a chafed signal wire contacting bare metal, a failed switch internally shorted to its own ground r...

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