This is about a useful as a noid light. All it tells you is that some signal is being sent (and voltage is not a good indicator as injector signals are DYNAMIC and constantly changing with engine MAP table info).
DDT was discontinued in 2006. It was replaced with the Computer Diagnostic System, which has now been replaced by CDS G3-2019. Your dealer should be using one of the later two.
Be sure to get printouts of the Run History, Freeze Frame (Fault) History, and Fault Second Counters. You can always post those for review if needed.