I replaced the EGR valve because I got a code 32 and 51. The codes are still there. How long do I have to wait for the computer to realize that the EGR has been replaced? Should I disconnect the battery overnight so it resets itself or does it take like 500 miles to figure it out?

 

The books say it can take up to 100 key on/offs before the check engine light goes out, the codes should be gone. Just disconnect the battery for 5 min. and then reconnect it and everything should be ok. If not, then there is still a problem. All the codes tell you is that that particular circuit has fallen out of it's operational parameters. It does not mean that the sensor/valve etc. itself is bad, but most of the time that is what is wrong. It could be the wiring to or from the sensor or just a bad or dirty connection.