CAN network

U0170 — Lost Communication with Restraints System Module

Severity: high Drive with care, to a shop

What U0170 means

A control module stopped receiving responses from the restraints (SRS/airbag) module on the CAN bus. This module normally talks constantly with other modules and monitors the airbag and seat belt pretensioner circuits. If communication drops, the module may have failed, lost power, or be unreachable because of a network problem. On some vehicles this code overlaps with U0151.

Symptoms

  • Airbag (SRS) warning light on
  • B-codes may be stored as well
  • Several warning lamps may light at once
  • Functions of the affected module are unavailable
  • Scan tool cannot communicate with the SRS module

Possible causes

  1. Failed SDM/airbag control module
  2. CAN bus wiring fault (open, short, chafed harness)
  3. Low battery or system voltage
  4. Previous crash or deployment not properly repaired
  5. Corroded connectors or terminals
  6. Power supply or ground fault at the module
  7. Another faulty module loading the bus

How to diagnose

  1. Scan all modules and map which ones are not communicating
  2. Check battery voltage and charging system output
  3. Inspect the SRS module connectors and harness (often under the seats or center console) for corrosion, damage, or prior repairs
  4. Check the module's power and ground circuits against the wiring diagram
  5. Measure CAN voltages and resistance at the diagnostic connector (about 60 ohms between CAN-H and CAN-L is typical)
  6. Test the CAN lines for continuity between the connector and the module
  7. Unplug suspect modules one at a time only if the manufacturer procedure allows it
  8. Disconnect the battery and follow SRS safety precautions before working on airbag circuits

Common fixes

  • Clean or replace corroded connectors and terminals
  • Repair damaged CAN, power, or ground wiring
  • Charge or replace the battery and fix any charging problem
  • Replace or reprogram the SRS module (per procedure, especially after a crash)
  • Replace a faulty module that is disrupting the network

Questions and answers

What does U0170 mean?

It means the restraints (SRS/airbag) module is not communicating on the CAN bus. That is why the airbag light is usually on.

Will the airbags work with U0170 set?

You should not count on it. The system may be disabled or faulty, so have it diagnosed promptly.

Can I just clear the code?

Clearing only helps if the cause was a one-time event such as a voltage dip. If the code returns, look for a power, wiring, or module fault.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.