Breakdown of koshoushindan ga owarimashita.

Questions & Answers about koshoushindan ga owarimashita.
It is read こしょうしんだん.
- 故障 = malfunction, breakdown, fault
- 診断 = diagnosis
Together, 故障診断 means something like fault diagnosis, diagnostic check, or troubleshooting, depending on context.
That’s right—normal Japanese is usually written without spaces.
So in natural writing, this would normally appear as:
故障診断が終わりました。
The spaces are just there as a learning aid to make the parts easier to see:
- 故障診断 = the diagnostic process / troubleshooting
- が = subject marker
- 終わりました = finished / ended
が marks the subject of the sentence.
Here, the thing that ended is 故障診断. So the structure is basically:
- 故障診断が = the troubleshooting / diagnostic process
- 終わりました = ended / finished
So が tells you what it is that has finished.