Flashing Digital Display and low fuel lamp

[drnuclear]

2003 Avalon with 145k, intermittent issues for the past two years ( since engine was rebuilt). It starts small, with the digital display backlight flickering, then the low fuel lamp starts flickering followed by the temp gage stepping in even increments until its pegged. By then the digital display is going on and off, and the fuel lamp is going on and off, followed by the engine running real rich and very rough. while the VSC light pops on, the check engine light doesnt, and there are no codes.
I've added more grounds and replaced the alternator cables, looked at all the fuses, replaced the digital display and the ECU, but nothing worked until I realized it never ran bad with the OBD II reader in place.
So I start it, it runs a little while before the lights start flickering, and shortly its into full on off mode again and running rough. plug in the OBD II and its smooth as silk, no flashing lights. Unplug it, and 12 seconds later it gets back into flickering etc, stops as soon as the OBD II is plugged in again.
I am guessing at this point that there is a ground or power loss somewhere that the OBD II bridges? or does it force the ECU into a diagnostic mode?

[feltonite]

Hi Doc,
I had very similar problems with my 2000 Avalon.
Eventually found that someone had removed both grounds that attach to the intake plenum, just above the PCV. One wire went to the strut tower, the other appeared to go through the firewall. Cleaned the connections, re-bolted to intake, no CEL and runs perfectly.

[drnuclear]

Thanks for the reply. While I havent found where the ground was lost yet, I did verify that the signal ground was not grounded. Once I added a ground, everything was fine again.