Code Definition

B0238 — Air Flow Control Circuit Range/Performance

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

About B0238

B0238 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 B0238 is stored, the module has detected a signal or supply voltage lower than the expected operating range; and a plausibility fault — the measured value is in the electrical range but is not consistent with expected operating behaviour.

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 B0238 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

This DTC is set by the HVAC control module when it detects a range or performance issue in the air flow (mode) door actuator circuit. The mode door actuator directs airflow between the various outlets — defrost, dash vents, and floor — and is driven by a small electric motor with an internal feedback potentiometer. The module commands the actuator to specific positions and watches the feedback signal to confirm correct movement; if the door responds too slowly, fails to reach the commanded position, or the feedback voltage falls outside the expected range, the code is set. When this fault ...

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