What Does U0171 Mean?
Communication with restraint system sensor B has been lost on the vehicle network. This sensor is typically another impact sensor (side, front, or rear depending on vehicle architecture) that monitors collision forces.
Safety Warning
Compromises airbag deployment capability in crash events. Critical safety system malfunction requiring immediate attention before vehicle operation.
Common Causes
35%
Defective impact sensor B with internal circuit failure or connector contamination
30%
Wiring harness damage between sensor B location and airbag control module
20%
Ground circuit fault at sensor B mounting location or chassis ground point
10%
CAN bus communication line fault (short to ground, short to power, or open circuit)
5%
Airbag module communication port failure or internal processing fault
Diagnostic Steps
1
Step 1: Locate sensor B using service information and inspect for physical damage, connector integrity, and environmental contamination
2
Step 2: Test power supply (typically 5V reference) and ground continuity at sensor B connector using digital multimeter
3
Step 3: Check CAN bus signal integrity using oscilloscope or multimeter to verify proper voltage levels and waveform on communication lines
4
Step 4: Perform continuity test from sensor B connector pins back to airbag control module connector to identify open circuits
5
Step 5: Clear codes and monitor live data for sensor B communication status; swap sensor if all circuits test properly
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
Communication with restraint system sensor B has been lost on the vehicle network. This sensor is typically another impact sensor (side, front, or rear depending on vehicle architecture) that monitors collision forces.
The most common cause of U0171 (Lost Communication With Restraints System Sensor B) is: Defective impact sensor B with internal circuit failure or connector contamination
Typical repair costs for U0171 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Compromises airbag deployment capability in crash events. Critical safety system malfunction requiring immediate attention before vehicle operation.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U0171 to identify the root cause.
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Quick Info
Category
Network
System
Supplemental Restraint System (SRS/Airbag)
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
