U0171 — Lost Communication With Restraints System Sensor B

U0171 — Lost Communication With Restraints System Sensor B. A fault in the airbag / restraint system (SRS). Short, gentle driving to a shop is usually possible. Typical causes: depleted backup battery or low system voltage, SRS control module fault or stored crash data, faulty impact or occupancy sensor.

vehicle network

Is it safe to drive?

Drive with caution The car drives normally, but with the SRS light on the airbags may not deploy in a crash. Treat it as a safety-critical repair: fine to drive to the shop, not fine to ignore for months.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm U0171 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many U0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the airbag / restraint system (SRS) for damage, corrosion, chafing or poor contact.
Subsystem check Read the SRS module with a scanner that supports airbag systems — generic OBD2 readers cannot see these codes.
Subsystem check Inspect under-seat connectors — they are often disturbed by seat movement or cleaning.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm U0171 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for U0171 (parts and labor, USD, independent shop rates): SRS module reset or replacement: $300–$1,000; Replace a sensor or clockspring: $150–$500; Reconnect or repair SRS wiring/connectors: $80–$250. Overall, fixing U0171 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

Will U0171 clear itself?

Sometimes U0171 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What is the most common cause of U0171?

The most common causes are: depleted backup battery or low system voltage, SRS control module fault or stored crash data, faulty impact or occupancy sensor.

How do I diagnose U0171 myself?

Start with a scan: confirm U0171, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the airbag / restraint system (SRS), and verify the suspect component against live data before buying parts.

Is it safe to drive with U0171?

The car drives normally, but with the SRS light on the airbags may not deploy in a crash. Treat it as a safety-critical repair: fine to drive to the shop, not fine to ignore for months.

What does OBD2 code U0171 mean?

What does U0171 mean?

U0171 is logged by the onboard diagnostics when the airbag / restraint system (SRS) does not behave as expected. The official definition is “Lost Communication With Restraints System Sensor B”. This is a vehicle network category code.

The module monitors this system continuously while driving. When readings fall outside the expected range for a defined number of drive cycles, it stores U0171 and switches on the warning light. Freeze frame data saved with the code shows the exact conditions — rpm, load, temperature, speed — at the moment the fault was detected, which is the best starting point for diagnosis.

Common symptoms of U0171

no other driving symptoms
airbag system disabled message
airbag (SRS) warning light on

What causes U0171?

failed clockspring (driver airbag circuit)
SRS control module fault or stored crash data
damaged wiring under seats or in the steering column
depleted backup battery or low system voltage
faulty impact or occupancy sensor

How to diagnose U0171

Connect an OBD2 scanner, confirm U0171 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many U0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Visually inspect the wiring harness and connectors related to the airbag / restraint system (SRS) for damage, corrosion, chafing or poor contact.
Read the SRS module with a scanner that supports airbag systems — generic OBD2 readers cannot see these codes.
Inspect under-seat connectors — they are often disturbed by seat movement or cleaning.
Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm U0171 does not return.

How to fix U0171

Start with the cheapest and most common causes before replacing expensive parts:

SRS module reset or replacement — $300–$1,000
Replace a sensor or clockspring — $150–$500
Reconnect or repair SRS wiring/connectors — $80–$250

How much does it cost to fix U0171?

Repair cost depends on which component actually failed. Typical scenarios for U0171 (parts and labor, USD, independent shop rates):

SRS module reset or replacement: $300–$1,000
Replace a sensor or clockspring: $150–$500
Reconnect or repair SRS wiring/connectors: $80–$250

Overall, fixing U0171 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can you drive with U0171?