U017E–U017F Lost Communication With Seat Belt Pretensioner Module 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 |
|---|---|---|
U017E | Lost Communication With Seat Belt Pretensioner Module A | Safety system |
U017F | Lost Communication With Seat Belt Pretensioner Module B | Safety system |
The definition
U017E: Lost Communication With Seat Belt Pretensioner Module A.
U017E 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.
What actually causes this on a VAG
U017E is the airbag control unit reporting that it has lost contact with one of the seat belt tensioner control modules. It is not a fault with the belt webbing, the buckle or the reel mechanism. It only applies to cars fitted with electric, reversible belt tensioners - the type that gently take up slack when the car senses an impending impact and let go again if nothing happens. On VAG that means Audi pre sense and the equivalent pre-crash function on MQB cars (A3 8V, Golf 7, Leon 5F, Octavia 5E and relatives). On those cars the airbag control module -J234- drives a small control module at each front belt retractor - -J854- on the left, -J855- on the right - over a LIN line, and U017E means one of them has stopped answering. Because it is a LIN link from the airbag module to that one unit, this is not a whole-car network problem and chasing the main CAN bus or the gateway will waste a day. Expect the airbag warning light on and that tensioner out of action. Treat it as a live restraint fault: in a crash the system may not do everything it was designed to do. It is not a light to clear and forget. If your car has ordinary pyrotechnic pretensioners with no control module of their own, this code does not apply to it at all.
Most likely causes, in order
- The connector and loom at the belt retractor, behind the B-pillar trim. The tensioner module lives with the belt retractor, normally behind the B-pillar trim, and its wiring runs down the pillar and along the sill. B-pillar or sill trim removal, a seat swap, an accident repair, or a dashcam or stereo cable routed down the pillar all put that plug and its wire at risk. With the battery disconnected, check the connector is fully latched and that the wire is not pinched or chafed where the trim clips back on.
- A weak battery, a recent flat or a jump start. Modules commonly log lost-communication faults when supply voltage dips, and the entry can survive long after the electrical problem has gone. If the fault is stored as sporadic or intermittent, charge the battery properly, clear the code with a tool that can actually access the airbag system, and see whether it comes back before touching anything else.
- Water reaching the sill, footwell or connector. Blocked plenum and pollen filter drains, sunroof drains and failed door membranes wet the front footwells and the base of the B-pillar, which is exactly where this loom runs. Press the carpet underlay hard with your palm and look for damp, staining or green corrosion on the pins.
- Failure of the tensioner module, or an open LIN line to it. The unit itself does fail, and so does the single LIN wire that feeds it. Both come last, and confirming either needs a scan tool that can properly interrogate the restraint system and check power, earth and the LIN line at the module connector.
Worth knowing: Never unplug or reconnect restraint connectors with the battery connected - switch off, disconnect the battery, wait several minutes, and only then work behind the trim. Note also that many cheap code readers cannot see or clear airbag-system faults at all, so "the light is still on after I cleared it" usually means the fault was never cleared. If a tensioner control module is replaced it needs its basic setting running with a proper tool before the system is right again. And an airbag warning light that indicates a system malfunction is an MOT failure - a major defect - on any car fitted with an electronic restraint system.
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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Common questions
What does U017E mean?
U017E means Lost Communication With Seat Belt Pretensioner Module A. This module has stopped talking on the car's data network, so nothing else can hear it.
Can I drive with U017E?
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.