I have had a check engine light that would come on ever 90 to 100 miles with a p0021 code. I would turn it off and drive another 100 miles since it's only my weekend car and it would last about a month. Every once and a while a battery code will come up and sometimes a vehicle speed sensor code but not all the time.

With the nice weather I decided to replace both vvt solonoids thinking that would correct the issue but I only made it to approx 120 miles and I got the p0021, p1721 vehicle speed sensor, and c1109 battery voltage codes.

I monitored the voltage and every few seconds the voltage running drops to 13.5 to 13.8 volts.

Do you think this is a alternator issue or something worst? Car always starts but every once and a will it will have a long crank about once a month.

My gauge cluster is failing or I think it is because the battery and break light above come on lightly some times but if you hit the dash they go out. I just wanted to state this.