How to fix Gm trouble code 21

What is your question?

I got cool 21 on my 1990 Chevy S 10 so I just replace the sensor but it still has the same problem with the Kranks with no start it’s got like extended extended cranking it doesn’t start it sounds like he doesn’t want to no power or something

What makes this problem better or worse?

No but I will say that everything was fine until I change the water pump

How long has your 1990 Chevrolet S10 had this problem?

2 weeks