Hi guys,
Legion JD and Walt - I have the chips on hand to repair the AIU board. I can make the repair for $50+shipping.
Legion JD - Don't give up on the AIU just yet. There's another possibility you should check first. As MTH told you, if a WIU is connected via the USB port on a Rev. L TIU, it will provide power to run the main processor. However, it will not power the AIU's or even read the presence of the AIU's. This makes the power up sequence VERY important. If the WIU is on and you then bring up power on the Z-4000, the TIU won't read the presence of the AIU and you'll get the error message posted above.
Try the following...
1 - Disconnect the WIU/TIU USB cable.
2 - Power up the TIU via the Z-4000.
3 - Connect the USB cable.
4 - Power up the WIU and wait 1 full minute for the WIU to boot.
If the AIU is still functional, the TIU will now find it and the error message should go away. If not, the AIU probably was damaged.