Check Engine Lite. No Codes

[57FleetsideC4]

Hi, I am doing a 57 chevy pickup with a 6.0 LQ4, 4L80E. I also have a Dakota Digitial Dash with the BIM module to pick up data from the PCM for the dash. I got the truck started only for about 15 seconds and the check engine lite is on with no codes stored. I did unplug the PCM and reconnected power and the check engine lite is not on so that tells me the wire to the lite is not grounded. Has anyone ran into this? This is the first LS conversion I have done so all new to me. Thank You Steve