Code Definition

B1921 — Airbag Diagnostic Monitor Ground Circuit Open

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

About B1921

B1921 is a manufacturer-specific body diagnostic trouble code recorded for Ford vehicles. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B1921 is stored, the module has detected an open (broken or disconnected) electrical path 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.

B1921 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) continuously monitors the integrity of its own ground reference circuits to ensure reliable airbag system operation. DTC B1921 is set when the RCM detects that the diagnostic monitor ground circuit is open or has a resistance higher than the calibrated threshold (typically greater than 100 ohms) between the ground reference pin and chassis ground. This circuit provides the stable ground reference used by the RCM to evaluate squib circuit resistance and crash sensor signals, so a degraded ground compromises the entire system's diagnostic accuracy. When this c...

Join TaT to view the complete code information and diagnostic details.

Quick Facts