Quote Originally Posted by dom14 View Post
When the voltage drops to 13.1v, open up the bonnet & check the voltage at the battery & alternator B+ output on the alternator.
Use a known accurate multimeter, and see that reading is consistent with the ECUtalk reading.

What issues are you having other than voltage showing too low?
Have done that Dom, and the voltage fluctuates on the meter as well. I checked the wires on the plug that connects the alternator to the wiring loom and one of the wires was corroded so I cut it off and soldered it back together. This made no difference, however I did start the car without the plug connected and it was reading 15.9 volts on the ECU Talk and meter. . . . . needless to say I shut the engine off quick smart. It appears as though there is a voltage regulator somewhere in the wiring loom that my be the issue. It's off to the mechanic tomorrow for a yearly fluid drop so they might be able to diagnose the problem.