What Does B0091 Mean?
This code indicates the restraint control module (RCM/SRS module) has detected a fault condition with the left side impact sensor number 1, which monitors lateral collision forces. The sensor may be reporting out-of-range values, intermittent signals, or communication failures. This subfault designation typically means a secondary or related issue within the primary sensor circuit has been detected by the supplemental restraint system.
Safety Warning
The vehicle is unsafe to drive as side airbags may not deploy properly in a side-impact collision, or may deploy unexpectedly. This is a critical safety system failure requiring immediate professional diagnosis and repair before operating the vehicle.
Common Causes
45%
Faulty left side impact sensor internal failure or calibration drift
30%
Damaged or corroded wiring harness/connector at sensor location
15%
Poor sensor ground connection or broken ground wire
10%
Restraint control module internal fault or programming issue
Diagnostic Steps
1
Step 1: Perform visual inspection of the left B-pillar or door area where side impact sensor 1 is typically mounted, checking for physical damage, water intrusion, or collision evidence that may have damaged the sensor
2
Step 2: Locate and inspect the left side impact sensor connector for corrosion, bent pins, moisture, or loose connection; disconnect and reconnect to ensure proper seating while examining terminal condition
3
Step 3: Using a digital multimeter, verify sensor power supply voltage (typically 5V reference) and ground continuity at the sensor connector with ignition on; check resistance values against manufacturer specifications (typically 1-3k ohms for accelerometer-type sensors)
4
Step 4: Check wiring harness continuity between sensor connector and RCM using wiring diagram, testing each circuit individually for opens or shorts to ground/power; wiggle test wires while monitoring for intermittent faults
5
Step 5: If all circuits test normal, substitute a known-good side impact sensor or monitor live data from the sensor using advanced scan tool to verify erratic signal output indicating internal sensor failure
6
Step 6: Clear codes, perform RCM system relearn/calibration procedure if available, and road test vehicle while monitoring for code return; if code persists with new sensor and good wiring, evaluate RCM for replacement
Estimated Repair Cost
$200 - $800
Parts + labor, varies by vehicle and location
This code indicates the restraint control module (RCM/SRS module) has detected a fault condition with the left side impact sensor number 1, which monitors lateral collision forces. The sensor may be reporting out-of-range values, intermittent signals, or communication failures. This subfault designa...
The most common cause of B0091 (Left Side Restraints Sensor 1 (Subfault)) is: Faulty left side impact sensor internal failure or calibration drift
Typical repair costs for B0091 range from $200 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle is unsafe to drive as side airbags may not deploy properly in a side-impact collision, or may deploy unexpectedly. This is a critical safety system failure requiring immediate professional diagnosis and repair before operating the vehicle.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B0091 to identify the root cause.
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Quick Info
Category
Body
System
Supplemental Restraint System (SRS/Airbag)
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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