Renewing a seatbelt tensioner
First, disconnect the battery and leave it for 15 minutes before undoing any plugs. Reach underneath the seat and locate the connector plug for the seatbelt tensioner, then disconnect it and plug in another one. Reconnect the battery and see if the replacement tensioner extinguishes the SRS light on the dashboard.
On MGFS and TFS with a square key-fob (pre-53-plate models), the tensioner’s plug connector should be red. Later models with a round key-fob have a yellow connector.
Renewing a seatbelt tensioner requires the seat to be removed, by undoing the four Torx T50 bolts holding it in place. The seatbelt tensioner is held to the side of the seat with a single Torx T50 bolt. Do not undo the bolt that holds the tensioner and seatbelt socket to the mounting bracket.
When refitting the bolt with a replacement tensioner, apply a little thread lock.