U0177

Lost Communication With Restraints System Sensor H

Communication network (CAN bus) Generic OBD-II High

What it means

U0177 means the restraints (airbag/SRS) system has lost communication with one of its sensors, sensor H. The engine and brakes work normally, so the car still drives — but this is a safety code: with the sensor offline the airbags or pretensioners may not deploy correctly in a crash, and the SRS warning light will be on. It usually traces to wiring, connector, power/ground, or bus faults at the sensor, or a failed sensor.

High

Can I keep driving? The engine runs and the car drives, but this is a safety code — losing a restraints (airbag) system sensor can disable or impair airbag/pretensioner deployment in a crash. Get it fixed promptly.

Common symptoms

What you'll notice

Airbag/SRS warning light on
Restraints system may be partly or fully disabled (airbags/pretensioners may not deploy correctly)
Other modules or the restraints control module logging lost-communication codes for the sensor
No drivability change — engine and brakes work normally

Common causes

Most likely first

Wiring or connector fault at restraints system sensor H (opens, corrosion, damage)Likely
Loss of power or ground to the sensorCommon
Communication/bus fault on the branch linking the sensor to the restraints moduleCommon
Connector unseated or damaged after service or a minor impactLess often
Failed restraints system sensorLess often

How to diagnose & fix

Work through it in order

Scan the restraints/SRS system with a capable tool to confirm sensor H is the one offline (a generic reader may not access SRS).
Follow proper SRS safety precautions (disconnect battery, wait the specified time) before probing airbag circuits.
Inspect the sensor's wiring and connector for damage, corrosion, or an unseated plug.
Check power, ground, and the communication line to the sensor against spec.
If wiring and supply are good, the sensor is likely failed — replace per the manufacturer procedure and clear the SRS code, then re-verify.

FAQ

Quick answers

Is it safe to drive with U0177?+

The car drives normally, but the airbag system may not protect you fully in a crash. That makes it a safety priority — have the restraints system repaired as soon as possible.

Can I just clear U0177?+

Don't rely on clearing it. If the sensor is truly offline the SRS light and code return, and the restraints system stays impaired until the wiring or sensor is properly fixed.

Related codes

Often seen with U0177

U0121Lost Communication With Anti-Lock Brake Sy U0126Lost Communication With Steering Angle Sen U0129Lost Communication With Brake System Contr U0151Lost Communication With Restraints Control

Read & clear U0177 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

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✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX