U0170–U0177 Lost Communication With Restraints System Sensor A
This module has stopped talking on the car's data network, so nothing else can hear it.
Can you drive it? This is a restraint-system fault. The airbag or belt tensioner may not deploy in a crash, and in some failure modes may deploy when it shouldn't. Have it looked at before carrying passengers.
Which code is which
Same fault, different cylinder or bank — diagnosed the same way. Several set together usually means one shared cause.
| Code | Definition | Severity |
|---|---|---|
U0170 | Lost Communication With Restraints System Sensor A | Safety system |
U0171 | Lost Communication With Restraints System Sensor B | Safety system |
U0172 | Lost Communication With Restraints System Sensor C | Safety system |
U0173 | Lost Communication With Restraints System Sensor D | Safety system |
U0174 | Lost Communication With Restraints System Sensor E | Safety system |
U0175 | Lost Communication With Restraints System Sensor F | Safety system |
U0176 | Lost Communication With Restraints System Sensor G | Safety system |
U0177 | Lost Communication With Restraints System Sensor H | Safety system |
The definition
U0170: Lost Communication With Restraints System Sensor A.
U0170 is a network code (communication between control modules), defined by the SAE standard - it means the same thing on any make of car, and any generic OBD-II reader will decode it.
What to check first
Cheapest and fastest checks first:
- Check power and earth at the module first - a module with no supply cannot answer.
- Check the two data-bus wires for continuity and for a short between them.
- Scan the other modules: if several report the same module missing, the fault is at that module rather than on the bus.
Reading the code is the easy part
A code names the circuit that complained. What tells you why is watching the sensor behind it while the engine runs — and that is where a code reader stops and a diagnostic tool starts.
VAGPULSE reads every module in a VW, Audi, Skoda or SEAT — not just the engine — shows the live measuring blocks behind this fault, gives you the freeze-frame conditions it was logged under, and clears it once you have fixed it. It also does what a generic OBD reader cannot on a VAG: service resets, coding, adaptations, and Stage 1–3 flashing with your original file saved first.
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Prefer to work on your phone? The VAGPULSE Android app is a free download and its demo mode runs against a sample car with no hardware at all, so you can see exactly what it reads before spending anything. Reading your car with it needs the VAGPULSE cable, which comes with the licence.
Common questions
What does U0170 mean?
U0170 means Lost Communication With Restraints System Sensor A. This module has stopped talking on the car's data network, so nothing else can hear it.
Can I drive with U0170?
This is a restraint-system fault. The airbag or belt tensioner may not deploy in a crash, and in some failure modes may deploy when it shouldn't. Have it looked at before carrying passengers.