Code Definition

B2559 — Aux A/C Blower Motor Relay Circuit Short to Battery

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

About B2559

B2559 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 B2559 is stored, the module has detected a short-circuit (voltage pulled to ground or to supply) in the monitored circuit; and a signal or supply voltage lower than the expected operating range.

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 B2559 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 auxiliary A/C blower motor relay supplies battery power to the rear or auxiliary HVAC blower motor when energised, allowing the rear or auxiliary HVAC system to operate independently of the front system. The controlling module (typically the climate control module or body control module) commands the relay coil on or off and monitors the coil control circuit for proper operation. DTC B2559 sets when the module detects that the auxiliary A/C blower motor relay coil control circuit is being held at battery voltage when it should not be, indicating a short to battery in the coil control wire ...

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