codes 12, 21, and 55

[LegionGS]

Hey guys its me again, trying to get my problem done and get back to the streets. Recently I got my my ECU replaced like a month ago and after that, I got some CEL codes (12, 21, and 55) I know that 12 and 55 are not important but the 21 is the H2O sensor. It can be the upstream or downstream right?? And to be honest both sensors (upstream and downstream) ARE BRAND NEW so I don't think they went bad or could be? thanks for looking

 

[Zufelt]

Hey guys its me again, trying to get my problem done and get back to the streets. Recently I got my my ECU replaced like a month ago and after that, I got some CEL codes (12, 21, and 55) I know that 12 and 55 are not important but the 21 is the H2O sensor. It can be the upstream or downstream right?? And to be honest both sensors (upstream and downstream) ARE BRAND NEW so I don't think they went bad or could be? thanks for looking

If it were me I would check both again, and clear the code to see if It shows up again, or was a fluke because I just changed them.