Code Definition

B1904 — Airbag Crash Sensor #2 Feed/Return Circuit Failure

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

About B1904

B1904 is a manufacturer-specific body diagnostic trouble code. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B1904 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.

B1904 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 Restraints Control Module (RCM, also called the Airbag Control Module or SRS module) monitors each remote crash sensor through a dedicated two wire feed and return loop, supplying a small bias to the sensor and reading its acceleration data while continuously checking loop integrity. DTC B1904 sets when the RCM detects a general failure on the feed or return circuit of Crash Sensor #2, which may be an open conductor, a high resistance connection, a short to another circuit, or a sensor that fails to respond to the bias supply. The specific physical location of Crash Sensor #2 varies betwee...

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