After running code above with:
A0 = Low
A1 = High
A3 = Low
A4 = Low
DVM readings on 74HC154:
Pin Voltage (V)
23 A0 3.53
22 A1 4.35
21 A2 0.0067
20 A3 0.0068
3 Y2 5.17
12 GND 0.0001
24 Vcc 5.17
16 Y14 5.17
18 E1 0.0001
19 E2 0.0001
Well A0 does not look Low. That is interesting. Any ideas?