I have a newly rebuilt 502 that I just finished installing. When I go to set the base timing with the scan tool the motor stalls. I can't restart the motor until I take it out of base timing mode and back into to normal mode. Any ideas? I have tried revving to 1800 and it still shuts off. The other motor goes into base timing mode without revving and works properly. The engine was at correct operating temp also.

Had 3.0 do that to me . Bad Module

make sure the scan tool is in service mode plus doing proper procedures accordingly to the service manual i the order listed.