Credit: eng92

This may be common knowledge but I did not see it in the stickies. There are three basic steps involved:

1) On the ECU connector, move the wire from pin 107 to pin 105.
2) Change out your 4-wire zirconia type rear O2 sensor for a 3-wire titania type.
3) Also must add rear O2 sensor signal ground from ecu pin 112 to engine grounds F18 and F19 on intake manifold collector.

Please be aware that you cannot sub a 3-wire zirconia type sensor in place of the 3-wire titania. The two types work completely differently. The zirconia type generates a voltage depending upon O2 levels. The ECU expects to see a fluctuating voltage from 0-1.0 V.

The titania type sensor changes in resistance depending on O2 levels. The ECU measures the voltage drop across this resistance. It expects a voltage fluctuating between 0-2.2V. If the ECU does not see the specified voltage fluctuation after a given time period, it will throw the P0136 code and give you a CEL.

Some of you may have discovered that the rear O2 sensor bung on a 98 is an 18mm thread while the one on a 96 is 12mm.

There are three options for sensor replacement:

1. Buy a 12mm, 3-wire titania type for a 96 and machine an adapter for it to fit the 18mm threaded bung.
2. Weld a 12 mm bung on your exhaust and use the 96 sensor.
3. Buy an 18mm, 3-wire titania type sensor. Easier said than done. Not used on any North American production cars that I am aware of. NTK Europe makes them but NTK North America does not. All of the 3 wire titania ones over here are 12mm.

I believe I found one through Oxygensensors.com. It is Walker p/n: 250-23881. It is a universal type, so you will have to cut the connector off of your factory sensor.

I know someone is going to ask the question: Will this work on a 99???

Short answer: I do not know.
Long Answer: I know the 99 uses a four-wire 18 mm zirconia type like the 98. The nissan p/ns may be different but that just means the connector or length of wire attached to the sensor is different. You would be replacing it with a universal so that does not matter.

I have FSMs for 96 and 98, not 99. The pin-out on the ECU may be different. If someone wants to supply me with the schematic for the rear O2 sensor circuit, I can let you know.

I apologize for the long post, but since there is a GD for JWT ecus going on right now, I figured this would be useful info for some of us 98s.

*********UPDATE*********
New O2 sensor finally arrived on Friday – installed it Sunday night

Problem – I am not picking up any voltage output from it on my OBD2 scanner.

A quick check of the 96 ECU schematic reveals the problem. The ECU requires a separate signal ground for the rear O2 sensor to be on pin 112.

Damn 3 wire sensors – the four wire types have a built in signal ground so no separate wire is necessary.
Time to hit the wrecking yard again. Probably the best place to get some of those “fancy” female terminals that go inside the ECU harness connector.

*********UPDATE*********

CODE P1220 GONE AS WELL

CODE FREE AND READY FOR EMISSIONS TESTING

Wired the FPCM and dropping resistor in on Saturday. Had to tun two new wires from the ECU to the left rear quarter where the modules are located. Some minor re-wiring of the body grounds and fuel pump were also required.

For all you 98s, this step should only be necessary if you have a 95/96 ECU out of a cali-spec or Canadian maxima and are getting the P1220 code.

Spare ’96 ecu will arrive at Technosquare today.

For any of you 98 cali-spec owners looking to convert to a 95/96 ecu, I have a whole harness full of ecu pins available. I can pop a couple in an envelope with ~24″ of wire attached and mail them out.

*********UPDATE*********

Just an update that may save some people some money.

Before going out and buying the titania 02 sensor:

1) On the ECU connector, move the wire from pin 107 to pin 105. There should be no existing wire in 105.

2) Ground ecu pin 112 (this is the rear 02 sensor ground)

I believe Dandymax just carried out the above two steps and it got rid of the P0136 for him. If it doesn’t work for you, then you will have to buy the sensor.