2001 Volkswagen Jetta Supply Voltage Low & Circuit Malf

Hi,

I am seeing the following error codes:

P0100 - Mass or Volume Air Flow Circuit Malfunction
P0110 - Intake Air Temperature Circuit Malfunction
P0115 - Engine Coolant Temperature Circuit Malfunction
P0120 - Throttle/Pedal Position Sensor/Switch A Circuit Malfunction
P1600 - Power Supply (B+) Terminal 15 Low Voltage

Any suggestions what may be causing this?

The only information I could dig up that may be related is from this forum post: http://www.bba-reman.com/forums/topic66546-1-1.aspx

Should I be checking my ECU first? Could it be anything else?