B29A2

Code

Generic B — Body

Airbag Control Module Communication Fault

Brand: Generic

Type: B — Body

Views: UK: 6 EN: 22 RU: 10

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Faulty airbag/supplemental restraint module (SDM)
Broken, corroded, loose, or shorted wiring/connectors to the module
Loss of module power or ground (battery/ignition feed, ground strap)
CAN/LIN bus fault, high bus error rate, or failed termination resistor
Fault in another module on the same network causing bus contention
Intermittent connector contact (water intrusion, pin damage)

Symptoms

Airbag warning lamp illuminated (SRS light on)
Possible disablement of airbags/pretensioners (lamp may indicate system fault)
Loss of certain safety features or faulted crash data storage
Other networked modules showing communication errors or warning lights

What to check

Read and record all DTCs and freeze frame data with a capable scan tool that supports SRS/airbag module functions
Verify battery voltage with ignition on and engine off (nominal ~12 V); check for recent battery disconnect or low charge events
Visually inspect the airbag module connector and harness for corrosion, damage, bent pins, or water intrusion
Check module ground(s) and power feed(s) for proper continuity and secure connections
Scan CAN/LIN bus for other U- or B-codes and check message traffic for the airbag module (presence and frequency of its messages)
Inspect nearby modules and wiring for signs of damage from accidents or repairs

Signal parameters

Airbag module supply voltage (nominal battery voltage with ignition on)
Module ground continuity/resistance to chassis ground
CAN High and CAN Low idle voltages (~2.5 V typical) and CAN differential activity
Message frequency (packets/sec) for the airbag module on the network as seen by a scan tool or oscilloscope
Bus fault counters or error frame counts if supported by scan tool

Diagnostic algorithm

Retrieve all SRS and network DTCs and notes; record freeze frame and occurrence conditions.
Check battery state and confirm adequate voltage; if low, charge or replace battery before continuing.
Follow vehicle manufacturer SRS disable procedure (disconnect battery and wait specified time) before touching airbag connectors.
Visually inspect module connector and harness for corrosion, damage, bent pins, or moisture; repair any damage and secure connectors.
Reconnect battery and use a scan tool to monitor live CAN/LIN data; verify whether the airbag module is transmitting and receiving messages.
Verify power and ground at the airbag module connector (voltage and continuity). Repair any open/poor circuits.
Check termination resistance on the CAN bus and inspect other modules on the same bus for faults; isolate segments if necessary to locate short or failing node.
Wiggle-test wiring harness while monitoring communication to find intermittent faults; repair harness or connector as required.
If wiring and power/ground are good and the module does not communicate, check for required reprogramming or software updates; consult manufacturer service information about cloning/programming procedures.
Replace the airbag control module only if confirmed failed; perform any required module coding, calibration, and full system checks, then clear codes and verify repairs under driving/ignition cycles.
After repair, verify diagnostic trouble codes stay cleared and confirm SRS lamp extinguishes and system self-checks pass.