Hey guys, I have a 1990 chevy c1500 with a 1227747 and 305 that I rebuilt about 30k miles ago. I have been modifying my proms for about 6 years now.

I found an issue recently while trying to get the hiway lean cruise mode to work where something that I am changing makes my TCC output like blink quickly rather than coming on. I have an LED wired to the TCC pin on the ALDL connector (had this since before I was modifying stuff, works great). The output blinks when you'd expect the TCC to come on but it never goes solid. I worry that this may be screwing up the transmission so I pull over and load an older BIN into it and everything is fine. My thinking is that there is some kind of address problem on one of the parameters and something I am changing is overwriting some other value in the PROM.


Vehicle info:

305 with flat top pistons (9.5-10:1?), swirl port TBI heads, L03 cam, short stock fit headers, 3" straight exhaust, 700R4, 3.08 gears, 31" tires. No EGR, I am planning on making an EGR cooler type thing to work with the stock style valve but keep the nasty crusty stuff out of my intake

Background info:

I use the Ostrich 2.0 and tunerpro RT to make my adjustments. I started out erasing and burning proms the old way since I had the equipment at work.
I am an electrical engineer that writes code for embedded micros sometimes so I sorta know how these computers work.

What I'm trying to accomplish with this tune:

The truck had an ASDU labeled prom in it when I got it. Ran pretty OK. After the rebuild I wanted to fine tune the VE table and add a little timing to take advantage of the compression and make it idle better in open loop. I read the chip into tunerpro and all of my early tuning was based on that. Weird thing is my BIN does not match the ASDU bin that I've found online. Anyhow, more recently I decided to try something completely different. I downloaded the AJUK bin which is supposed to be for a truck like mine with the 305, 700R4 and 2.73 or 3.08 gears. It ran pretty good unmodified. I downloaded a BIN for the L03 on a different ECM, opened it with the right XDF, copied the timing table into excel, loaded my BIN back up with it's XDF and pasted that timing table in. That ran great! the BLMs were pretty dang good for stock. I added back in my A/C idle speed increase and tweaked the TCC rpms and speeds along with a few other things and it ran excellent. THEN I decided to give the hiway lean cruise mode a try since I drive about 25 miles of 60mph country roads to work every day. As soon as I enable everything for that I get this TCC output problem.