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DTC Troubleshooting
DTC B1157 (No. 1157): Air Bag Deployment Signal InputS7RS0BA204011
Wiring Diagram
Refer to “DTC B1150 (No. 1150): Air Bag Communication Circuit Malfunction”.
DTC Detecting Conditi on and Possible Cause
Flow Test Description
Step 1: Check DTC for SDM.
DTC Troubleshooting Step Action Yes No
1 Check air bag communication circuit
1) Turn ignition switch to OFF position.
2) Disconnect connector from SDM referring to “SDM
Removal and Installation in Section 8B”.
3) Disconnect connector from junction block assembly.
4) Turn ignition switch to ON position.
5) Measure voltage between “L29-37” terminal of SDM connector and vehicle body ground.
Is voltage 0 V? Go to Step 2. Short to power supply in
air bag communication
circuit.
2 Check air bag communication circuit
1) Turn ignition switch to OFF position.
2) Connect connectors to junction block assembly.
3) Turn ignition switch to ON position.
4) Measure voltage between “L04-2” terminal of junction
block assembly connector and vehicle body ground.
Is voltage 4 – 6 V? Go to Step 3.
Short to ground in air
bag communication
circuit. If OK, substitute
a known-good BCM
(included in junction
block assembly) and
recheck.
3 Check air bag communication circuit
1) Measure voltage between “L29-37” terminal of SDM
connector and vehicle body ground.
Is voltage 4 – 6 V? Substitute a known-
good SDM and recheck.
Open or high resistance
in air bag
communication circuit.
DTC detecting condition
Possible cause
Air bag deployment signal is fed from SDM to BCM. • Air bag component parts
• BCM malfunction
StepAction YesNo
1 DTC check of SDM
1) Check DTC stored in SDM re ferring to “DTC Check in
Section 8B”.
Is DTC B1021 detected? Go to “DTC B1021:
Front Air Bag Module
Deployed in Section
8B”.
Substitute a known-
good BCM (included in
junction block
assembly) and recheck.
