AFAIK, the one with one wire is the one for the gauge. The one with two wires is for the ECM. But that's based on more of an examination of the 96 Turbo diagrams and not actual experience as I've never dug into a 96 turbo before.

Testing:

1. Disconnect the wire from the sensor (the one wire sensor!) The wire color may be green (either dark or light) or brown. Book says at the sensor it is brown.

2. Gauge should read minimum.

3. Ground the wire you removed.

4. Gauge should read maximum.

5. Check for voltage at the gauge (power). If none, fix it.

6. Check continuity from gauge (S terminal, dark green?) to the brown wire at the sensor. If open, fix it.

7. Check ground on the gauge to body ground point(s) If open, fix it.

Peter