Hello, my name is Thom, I am having problems with my 1989 740. The check engine light came on, and I then tried to run diagnostic-starting with oil and other fluid reservoirs and then moved on to the On-board Diagnostic. The reader on these old Volvos can fail or so I'm told The OBD light sensor is showing a solid light with no flashing or sequence. I then used a method I have used in the past fearing that the diagnostic light was malfunctioning. I used a test light along with insulated wires with plugs to take over the circuit. The test light also showed a solid light as well. Does anyone have any ideas on what might be the problem.