As I just mentioned in another post (for the guy installing the AFR gage in Panama) there are two circuits - a heater and a sensor.
You can find out which one is which by turning the key ON and backprobing the pins for +12VDC - that's the one feeding power INTO the heater. Mark it (or write down the colour) and turn the key off.
Check the other three wires by colour, and match them up to the wires going into the TPS. One of them should match - this will be the sensor ground. Check for continuity between those two terminals, and mark the wire (or write it down.)
Take the other two wires, and check for one of them to have continuity to the chassis - this is the heater ground.
The other one is the sensor output.
Typically, the HEGO sensor heating element should show 5-7 ohms between the two heater terminals - if it's "open" (infinite resistance) or "short" (zero resistance,) it has failed. This does not mean a failed sensor entirely - but warmup mode and entry into closed loop operation will take much longer.
With the enging running, the sensor output terminals should show a value (full range) of zero to five VDC, but this value should show between 2-3VDC, with a mean of 2.5VDC (for AFR = 14.7:1 or thereabouts.) You are not likely to get a steady reading, since the HEGO sensor used as OEM is a "knuckle" type, which constantly switches back and forth. It may be easier to read sensor output using an analogue voltmeter (the one with the needle.)
With the 1996XJ, you may actually have TWO HEGO sensors - one in the manifold collector, and another downstream of the catalytic converter. Wiring for both should be similar, and can generally be inferred using the same tests and methods. It is common for the heater wires to be the same colour on the vehicle side of both harnesses, leaving only the sensor ground and sensor output to be determined individually.
5-90
