Matt81

I'm starting to dig into my project 88 Anniversary and stumbled across something I haven't been able to figure out through the FSMs and forum searches. Here it goes...

On the test drive today (its first since arrival as the brake booster was cracked, making stopping a chore!), I noticed the Upshift and OD lights did not light up. The overdrive appears to be functioning normally, as I could engage and disengage through the button on top of the gear shift. It also felt like the ECM was controlling the OD as well, but this seemed harder to confirm.

I had an Autoprom in the ALDL port while doing the test drive as I wanted to check if the BLM was indicating any lean or rich conditions. With the car powered on but not running, I could see the flag for overdrive toggling between On and Off when I pushed the button.

When the car is first started and the dash lights up, the Upshift and OD indicators illuminate. So the circuitry in the dash should be correct.

The FSM shows how the ECM controls the OD through the OD relay, but I couldn't find anything in the manuals about how that signal gets to the dash.

Thanks for any help!
Matt

Matt81

Forgot to mention, car runs ok (not great). No codes from ECM.

scorp508

This one is a bit tricky. The digi-dash gets a bunch of serial data from the ECM on pin D10. Two of the bytes of information are whether or not to turn on the OD light (if OD is active) and the upshift light based on the RPM parameters in the tune. Do your tripometer and gas mileage features seem to be working? If not it may be a clue the connection on that pin isn't very good.

There's more info here; https://www.corvetteforum.com/forums...post1597768204

Matt81

I'm glad you mentioned the gas mileage function. It did not work on this drive, but the trip meter did. Would the Autoprom plugged into the ALDL port have disrupted the signal?

I have to get the clutch figured out before any additional test drives. The one today was a little scary at times!

LWesthaver

When you are in ALDL mode, portions of the digital dash stop functioning. This is normal. Once you disconnect the ALDL reader from the ALDL port everything should start working again.

The digital dash shares the serial data line with the ALDL.

Matt81

That is what I was hoping for. Lots to troubleshoot on this car .It has had a very rough time of it.

By the way, I have been closely watching what you've been doing on the raspberry pi radio. Very cool!