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U0172 Generic (SAE) Basic entry

Lost Communication With 'Restraints System Sensor C'

Updated 2026-10-02 · Network communication (generic)

Severity
Medium
Typical repair cost
50 – 700 EUR
System
Network

What it means

U0172 is stored when a module on the vehicle network stops receiving messages from the 'Restraints System Sensor C'. The missing module may be unpowered, faulty or disconnected from the bus.

This entry is compiled automatically from the standard definition and typical diagnostic practice for this type of fault. A detailed, reviewed article is in preparation.

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Symptoms

  • Several warning lights on at the same time
  • Functions controlled by the affected module do not work
  • Scan tool cannot communicate with one module
  • Gauges dropping to zero or dashboard flickering

Common causes

  1. Blown fuse or no power supply to the 'Restraints System Sensor C'
  2. Poor ground for the module
  3. Damaged CAN/data bus wiring or connector
  4. Failed module
  5. Low battery voltage during cranking or after a jump start

How to diagnose

  1. Check which modules respond to a full system scan and which do not
  2. Verify fuses, power and ground at the 'Restraints System Sensor C' connector
  3. Measure CAN bus resistance between the two bus wires (about 60 ohms with the battery disconnected) and inspect the wiring
  4. Check battery voltage and charging system; low voltage causes many communication codes
  5. Replace or reprogram the module only after power, ground and bus wiring are confirmed

Frequently asked questions

Can I keep driving with U0172?

Usually yes for a short time, but expect reduced performance or higher fuel use. Have it diagnosed within a few days.

Will clearing U0172 fix it?

No. Clearing only erases the stored code; it returns as soon as the monitor runs again unless the cause is repaired.

Related codes

U0170U0171U0173U0174

Nearby codes in this group