why does check engine light, abs light off and on erratically.

Yes, intermittent speed sensor drop-out sure will cause the ABS to malfunction and the light to turn on/off plus the noise you're hearing .. However that's not why the check engine light is on .. Both problems require a scan test using an 'appropriate' scanner that has ABS live data capabilities... That will show WHICH sensor is causing the problem while test driving .. Then the check engine light problem can be addressed using same scanner... Most likely will have to visit a repair shop for this testing as not many other places/individuals are going to have an 'appropriate' scanner!