B0049 – Left Front Side Impact Sensor Circuit High
DTC B0049 indicates that the Airbag Control Module (ACM) has detected a high voltage condition in the left front side impact sensor circuit. The impact sensor provides collision information to the Supplemental Restraint System (SRS) module to help control airbag deployment decisions.
A high circuit condition means the sensor signal voltage is higher than the expected operating range, which may indicate a wiring or sensor problem.
Code Information
- DTC: B0049
- System: Supplemental Restraint System (SRS)
- Description: Left Front Side Impact Sensor Circuit High
- Severity: High (Safety Related)
Symptoms
- Airbag warning light ON.
- SRS warning message displayed.
- Side airbag operation may be affected.
- B0049 stored in the Airbag Control Module.
Possible Causes
- Short circuit to battery voltage.
- Damaged left front impact sensor.
- Open or damaged connector terminals.
- Incorrect sensor signal voltage.
- Water intrusion or corrosion.
- SRS module internal fault (rare).
Typical Wiring Diagram
Diagnostic Procedure
- Confirm DTC B0049 using an SRS diagnostic scan tool.
- Check for related SRS codes stored in the module.
- Inspect the left front impact sensor connector.
- Check wiring for short to battery voltage.
- Compare live data values with manufacturer specifications.
- Repair damaged wiring or replace faulty components.
- Clear codes and verify the repair.
Live Data Diagnosis (Advanced Scan Tool)
Advanced scan tools allow technicians to monitor SRS sensor information and identify whether the high voltage condition is caused by wiring, sensor failure, or module problems.
Accessing Live Data
- Connect the scan tool to the vehicle DLC port.
- Select vehicle make, model, and year.
- Open:
System → SRS Airbag → Data Stream / Live Data
Check These Parameters
- Left Front Impact Sensor Status.
- Sensor Communication.
- Sensor Voltage Reading.
- Battery Supply Voltage.
- Freeze Frame Data.
- SRS Event Information.
Live Data Interpretation
- Voltage Higher Than Normal: Check for short to battery voltage.
- No Communication: Inspect wiring and connectors.
- Normal Data But Fault Returns: Suspect sensor or SRS module.
- Changing Values: Check for intermittent wiring faults.
Important Note
Wire colors, connector pin locations, sensor mounting position, and electrical values vary between vehicle manufacturers. Always follow factory repair information before testing SRS circuits.
Can You Drive With B0049?
The vehicle may still drive normally, but the SRS system may not function correctly during a collision. This fault should be repaired as soon as possible.
Estimated Repair Cost
- Connector repair: $20–80
- Wiring repair: $40–150
- Impact sensor replacement: $80–300
- SRS module repair/replacement: $300–900
Related DTCs
Frequently Asked Questions
What causes B0049?
The most common causes are wiring shorts, connector damage, or a faulty impact sensor.
Can live data detect B0049?
Yes. Advanced scanners can show sensor voltage and communication status.
Should I replace the sensor first?
No. Always test wiring and live data before replacing the sensor.
OBDSpark Technician Tip: Never use a test light or apply external voltage to SRS circuits. Always follow proper airbag safety procedures.