Code Definition

B1820 — Wiper Rear Motor Up Relay Coil Circuit Short To Battery

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

About B1820

B1820 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 B1820 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.

B1820 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 the rear wiper motor up relay coil control circuit on Ford vehicles equipped with a rear wiper system. DTC B1820 is set when the BCM detects that the up relay coil control wire is shorted to battery voltage, meaning the line that should be at near 0V when the relay is commanded on (or pulled high through the BCM internal pull up when off) is reading battery voltage continuously. This typically results from chafed insulation allowing the control wire to contact a powered conductor, a wiring repair error swapping power and signal pins, or an internal short ...

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