Do a search for " afx wideband " $260-$300

Completely stand alone. Connect to the battery, run the display into the passenger compartment and run the sensor into the tailpipe (the wires are long enough). If you plan to drive it that way, you will need to clip the lead to the tailpipe to keep the sensor from backing out. I used a hitch pin clip and some bailing wire. The sensor is heated so you will have to disconnect the sensor at the battery when done. When we add these to the race cars, we drill a second hole into the exhaust system, weld in the included bung and connect the wideband there.

Back to your issue. Can you define all of the sensors and devices that regulate the fuel? I can't tell from reading this if you have pulled the connector to the computer and checked the sensor readings there. I mention this because the wires' insulation may have suffered from the overheating causing a short in the harness. You will only find this if you look at the inputs the way the computer sees them.

Check with everything plugged in and then check again by unplugging everything one by one. My MB document recommends that you disconnect the battery before you unplug the computer from the connector and don't connect the battery again until the computer is back in line.