2001 Jetta P0100 & P0400 Trouble codes

We have a 2001 Jetta (4 cyl auto) that is giving me the following when we run a scan:
Vechical reports 3 stored trouble codes:
TC1 - P0100 Mass or volume air flow circuit malfunctionodes:
TC2 - P0400 Exhaust gas recirculation flow mal-function.

It does not list the third one???

Any suggestions as to what to do to fix these problems would be appreciated.

John

P0100 refers to the circuit malfnction, so you're first going to want to visually check the wiring to and fromthe MAF. Verify it's okay. Check pids for barometric pressure-should be 160 Htz at sea level and decrease as your altitude increases.
Start with that. The EGR code evidently means the PCM didn't detect any EGR flow when commanded. So again, checking visually first for any broken or wiring issues.
Start with visual checks

Thanks, we will check it out.