Code Definition

B2109 — Heated Wind Shield Relay Short to Vbatt (changed from Failure 2/6/97)

System: Body  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About B2109

B2109 is a generic (obd-ii standard) body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B2109 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.

Because B2109 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The Body Control Module (BCM) drives the heated windshield relay coil to control the heated windscreen element on vehicles equipped with this feature (commonly Ford, Jaguar, and Range Rover). DTC B2109 is set when the BCM detects that the heated windshield relay control circuit is shorted to battery voltage, meaning the control wire reads B+ voltage when the BCM is attempting to pull it to ground to energise the relay. The heated windscreen draws a heavy current and is typically switched on for a few minutes via a timed relay function. When this code is set the heated windscreen may stay on co...

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