Check engine comes on immediately after clearing codes???
 

Hi all,
I'm pulling a 0420 code on my 2001 crv lx(191k). After running cat cleaner through the system(no luck) I order both O2 sensors and asked the auto tech program at the high school I work at to install them(perhaps my first mistake). They did the work but after clearing the codes a strange thing happens, the check engine light comes back on within 10 seconds rather than after going through the drive cycle. After I got it home I disconnected the battery for 15mins to see for myself and sure enough, the check engine light came right back on.
What could be causing this? Did I mistakenly order an incorrect O2 sensor or were they installed incorrectly?
I've been mentally preparing myself for the possibility replacing the cat but this strange reaction from installing the O2 sensors has me confused.
Super appreciate any feed back!

welcome to the forum. a few items that aftermarket items work for a short time then fail, or fail from installations are sensors, transmission fluid, relays. honda must make them in their own shop and so far no one has been able to produce an exact oem product. sometimes you may be lucky and the aftermarket product will hold up for a while.

Did you read the code after the check engine light immediately came back?
Check engine light doesn't necessarily mean it is the same code???
More than likely is that the O2 sensors do not work right.