It is a unidirectional Zener-type transient suppressor in a DO-214AB (SMC) surface-mount package. The 40.2 V reverse standoff voltage places it on a 36 V or 42 V nominal rail, with a minimum breakdown of 44.7 V and a maximum clamping voltage of 84 V at the 119 A peak pulse current (8/20 µs waveform). That 1500 W peak pulse rating is the headline number for sizing the clamp against load-dump and inductive-load transients in an automotive ECU.
Package and footprint — DO-214AB SMC
It is a single-channel unidirectional device, so the cathode band or polarity marking must be observed during placement. The SMC body is larger than the smaller SMA/SMB packages, which helps with thermal dissipation during the pulse event.