Oxygen Sensor - 1 Wire to 4 Wire conversion?

[AndyTTR]

The 1UZ in the Supra is getting terrible fuel economy (worse than my Soarer which was heavier and an Auto). I think I may have damaged one of the oxygen sensors while installing the motor.

I ordered new universal sensors to suit the LS400, but it turns out the Aus spec. car got a 4 wire sensor instead of the 1 wire on the JDM cars. D'oh!

Anyway, I've done a bit of reading, and it seems that there are advantages to running a heated Oxygen Sensor over a non heated one - more consistent response, will reach the closed loop temperature threshold sooner than a non heated one, longer service life...

Obviously I'd have to wire up a circuit to run the heater element. The USDM UZZ30 wiring diagram shows that the heater is controlled by the ECU (HTL1 and HTR1). I will check it out, but I doubt my JDM ECU will have these outputs...

The sensor is grounded to the cylinder head which is easy enough...

If I connected the heater to IGN power so that it was running constantly, would this damage it?

I just wanted to get other people's opinions before I go ahead and do this. Would the conversion be worth the effort or just a waste of time?

Cheers.

[CrUZida]

Given the location of the o2 sensors on the 1UZ, I doubt a heated one will give any benefit.
They are only used in USDM cars for emissions purposes during cold starts. I'd be very surprised if it affected cruising economy.

That aside, hooking it up to ignition power is the norm.

[DX20VT]

They are only used in USDM cars for emissions purposes during cold starts. I'd be very surprised if it affected cruising economy.

That aside, hooking it up to ignition power is the norm.

Almost 99% of the jap import stuff we see here in NZ have 4 wire sensors.

I'd be very surprised if a jap spec 1UZFE did not run a 3 or 4 wire sensor.


The main reason the sensor heater runs thru the ECU is so that is can monitor the current as much as control it, so it knows when the sensor heater is buggered and will make the sensor read inaccurate.

Most sensors will run with the heater powered up of ign all the time no worries.

Matt

[CrUZida]

I'm yet to see an early 1UZ with more than a single wire sensor.
I've mainly played with '90-'92 stuff though.

[TERRA Operative]

You may also find the 4 wire sensor is grounded through the case too, making the ground wire somewhat redundant if the case has a good connection. Best to check first though. (Or just run a dedicated ground back to the ECU ground to be sure).