First, thank you for an invaluable forum. I used to post under the name Hexagram13, but I don't have access to that email any longer. I still have the 1999 C5 that yall helped me hop up in 2005.
The car has been sitting for years. I drove it 6 months ago after getting old fuel out of it. However, now I'm getting stall after about half a second of running.
I've done a lot of research today, and I wanted to ask for some guidance on next diagnostics. I really prefer not to jack the car and remove the wheel to get to the PCM, but that may be my required next move.
I am getting PCM-No Comm with several common serial bus errors. I checked Pin 2 in the OBD port and I'm getting <1v DC there. My reader can't pick up. From the dash, I will put the pulled codes below. I pulled both star connectors one at a time, and both together with no change in the status of the OBD port or starting. I have cleaned the grounds by the left and right headlights as well as the one under the battery that the PCM connects to. The PCM ground is nicked with copper showing, probably from me putting the battery in and out while working on the car. I'm looking at the schematic for the serial data port, but I'm not really seeing a common failure I should explore next. I could go for PCM or any of the door modules, but I hoped for some guidance. I also removed what looks to be aftermarket insulation pierce connectors around the BCM.

Aftermarket connectors disconnected
Thank you!
10-PCM No Comm
28-TCS C1242H; C1255H; U1255HC
38-RTD No Comm
40- BCM U1255HC
58-SDM U1000HC; U1016HC
60-IPC No Codes
80- Radio No Comm
99 HVAC No Codes
A0-LDCM U1064H
A1-RDCM U1064H
A6-SCM B2605HC
B0-RFA U1000HC

 

On a GOOD data bus with the key ON checking voltage at pin 2 the voltage should be fluxuating between 0.2 to 0.7 volts...if voltage steady and low near ground the data bus may be shorted to ground...take an ohm meter with battery disconnected and measure pin 2 to ground...resistance should be over 8000 ohms...if below 350 ohms that’s bad...if you remove both splice pack "combs' jumper the PCM to the BCM which are the dark green and light green wires...the car should start if BCM and PCM are good...if you think the PCM is bad jumper a wire from the dark green PCM wire to the purple wire which is the data bus wire (A) and if you can't communicate with your code reader which only talks to the PCM then the PCM is bad...you should check ALL PCM powers and grounds before condemning it…if you can communicate with the PCM then the BCM is bad…there are 4 wires which comprise the PCM ground…that ground is located on the engine block where the negative battery cable connects to.



https://www.youtube.com/live/f_NEEdg...xzZmhFGEKYDFti

 

G106.