This does not happen on a regular basis but on occasion when first starting the vehicle they do not flash in sync but a rapid vsc then abs

1) if I do not start the engine right away they will rapidly flash, key all the way on but has not engaged the starter.

2) I start the engine and they rapidly flash so I shut the engine off and restart they stop??

They never appear while driving just upon starting and not every time.

There are no codes showing on my scanner?

any ideas a search did not provide me with the info I am looking for

03 SR5 V8 76K on it

Bringing this back up from the dead, but was there any solution to this? Mine has the exact same symptoms. No CEL, no VSC off light, rapid flashing. I have found that occasionally I can wiggle some wires above the brake pedal and it won't do it, all connections seem fine though. Seems like it's happening more often. Not sure if this is a zero point cal symptom or just a loose connection somewhere.

Bumping this one... washed underneath my truck with a pressure washer and noticed this when I restarted it. I will say I have a spliced together abs/atrac wire on the front driver's side following a broken wire, compliments of the alignment shop. It's been working fine, however since the repair 6 months ago, including a couple of wheeling trips. I have a new one in the drawer, just haven't installed it. I might try swapping that out to see if by chance I got water on the connection. The lights are flashing really fast in an alternating fashion - Trac & ABS.

Update. I went ahead and swapped my abs sensor wire out and turned on the key to find the flashing continued. I unplugged the battery for a few minutes. Turned on the key and it was gone. Started the engine for a few seconds and it was still off. Turned key back on a couple minutes later and it was back. Then it occurred to me that when I was repairing the initial broken wire, a similar situation arose where I could not get the truck to let go of the flashing lights.. Although at that time it was a different set of flashing lights. What the common denominator was/is is the fact I have a Scangauge 2 plugged in. And although it isn't storing any codes, it seems to if not cause, certainly agitate these issues when I'm trying to hunt them down. I unplugged the Scangauge. Then I turned the key back on. Flashy lights gone. Plugged the Scangauge back in. Noticed all data strangely was now absent in the Scangauge, but no blinky lights anymore. I think for me from here on, first thing I will do is unplug the Scangauge if/when this occurs. What was the original cause? No clue. I've since driven 50 miles with no return of the blinky lights.

For future searches, I also noticed the issue was with my scan gauge. It happens occasionally, and if I unplug and replug my scan gauge it's gone. I don't drive it often, but I do this once every six months maybe. It must connect two pins of the OBD2 port when it's loose or something.