B1177: Right Pretensioner Stage 2 Open

Circuit fault

What B1177 means

Dual stage pretensioners fire in two steps so the system can match belt tension to the severity of the crash. Stage two has its own squib and its own circuit, which is why it gets a dedicated code. B1177 means the module found no continuity on that second circuit, so it can no longer promise the passenger belt will tighten the way it was designed to.

The pretensioner lives at the passenger seat belt retractor, in the pillar or on the seat frame depending on the design. Its connector sits close to the floor, close to the sill, and close to whatever gets tracked into the car. Both stages run through that same connector area, so a fault that affects only stage two often points at one damaged pin rather than the whole plug.

Common causes

• One pin backed out or corroded in the pretensioner connector while the rest of the plug is fine
• A retractor connector left unlatched after pillar trim or seat removal
• Harness chafe where the wiring passes through the sill or under the seat
• Water at the sill connector from a door seal or a wet carpet
• An open second stage squib inside the pretensioner assembly

Crash data or hardware fault?

This is a live circuit fault, so B1177 tracks what the module reads at this moment. Repair the open and the code stops setting. Crash data is the other kind of memory in these modules: written the instant a deployment happens, locked in, and not removable with a scan tool.

Does our reset clear it?

Resetting the module clears stored data, and on a car that has been in a crash that is exactly what is needed. It does nothing for an open stage two circuit. The module will measure that loop again and store B1177 again. Fix the connector, the harness, or the pretensioner before the module goes back in.

Which makes throw it

B1177 appears on Infiniti in our lookup. Dual stage pretensioners are common across restraint systems of this design, so a technician who has chased a stage two fault on another make will find the circuit laid out in a familiar way.

What to do next

Get to the passenger retractor connector and inspect every terminal rather than just reseating the plug, since a single backed out pin explains why one stage reads open while the other reads fine. Trace the harness where it exits the sill for chafe. If the connector and wiring are sound, the pretensioner assembly has an open squib and needs replacing. We stock genuine OEM seat belts and pretensioners. Related codes: B1150, B1209, B274D-11.