U0172 code meaning
Lost Communication With Restraints System Sensor C
What U0172 means
U0172 marks a lost link to restraint sensor C. Chrysler uses it for the first left side satellite acceleration sensor in the Jeep tables of NHTSA file PE11-019. The Wrangler JK has just this one sensor on each side, whereas Compass/Patriot, Liberty, Grand Cherokee and Commander add a second left unit reported as U0173. Bosch fits side sensors of this type to load-bearing parts such as sills, seat cross members and the B- or C-pillar, because a side impact leaves almost no crush space and the airbag unit must decide within a few milliseconds. With sensor C missing, left side and curtain airbag deployment may be degraded. An internal fault of the sensor appears as B1B72 instead. Water in the footwell or seat removal are typical triggers. No MIL.
U0172 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0172
- Airbag warning lamp on
- Left side and curtain airbag deployment may be impaired
- Fault can be intermittent with wet carpets or after rain
Common causes of U0172
- Most likelyWater in the left footwell or sill area reaching the sensor connector
- PossibleConnector disturbed during seat, carpet or trim removal
- PossibleLeft side satellite sensor failed after a side knock
- Less likelyAirbag control unit input or configuration faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Restraints system sensor cCrash signal wiring
What each part of U0172 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 72 | The exact fault in that area. |
What to do next
- Note U0172 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0172
What does U0172 mean?
U0172 means "Lost Communication With Restraints System Sensor C". U0172 marks a lost link to restraint sensor C. It is a generic code, so it means the same on every make.
Is it safe to drive with U0172?
U0172 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0172 fail an emissions test?
U0172 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U0172 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will U0172 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.