Code Definition

B0520 — Rear discharge temperature sensor signal error

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

About B0520

B0520 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 B0520 is stored, the module has detected a sensor-related fault — the reported value from the named sensor is out of spec.

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 B0520 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

DTC B0520 is a generic body code that indicates the HVAC control module has detected an invalid, erratic, or out-of-range signal from the rear discharge air temperature sensor. On vehicles equipped with rear or third-zone climate control, this NTC thermistor is mounted in the rear HVAC unit downstream of the rear heater core and evaporator, and the climate module uses its reading as closed-loop feedback to verify rear discharge temperature and trim the rear blend door position to match the rear setpoint. The code sets when the signal voltage is implausibly high (open or near-reference), implau...

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