Can anyone identify what this harness go to? 88TR

o2 sensors

 

The black and white two-pin connectors are a +12V and ground to run the internal resistance heater of each O2 sensor. The single wires with the male spade connector are where the single output wire from O2 sensors connect to send their "Lambda" signal to their respective injection ECU. Are there no O2 sensors mounted in the inlet of your aftermarket cats?

 

Welcome and congrats! Lets see some pix?

 

When cats overheat, the O2 sensors send a signal to your your overheat warning lights on the dash. Often removed or disabled to eliminate the warning light. Looks like your cats have a bung.

Overheated cats are typically caused by an over rich condition or cam timing that is off.

Check these root cause issues!

 

Because TR don't have any check engine lights. Without O2 sensors (or by unplugging the O2 sensors), it will run in open-loop mode like a KE-Jet without Lambda. It's not a common practice and usually only done if a car is having a closed-loop operation problem.

What they do have are cat over-temp "slow down" warning lights that should go thru a short self-test when you turn the key "on" -- i.e., they light up for a second, or two, and then go out. If it doesn't do this self-test (i.e., these slow down lights never come "on" at all), either the slow down ECUs have failed or someone has unplugged them (they are mounted on the backside of the small cover above the 1-6 Accumulator on the frame inside the RR suspension. These slow down ECUs use the thermocouple mounted in the pre-cat outlet (or cat outlet) to sense the exhaust gas temperature:
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These are an early style of the slow down ECUs where the thermocouple leads are attached by nuts/screws (the later style has a pigtail connector):
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This is the later style slow down ECU (with better connectors):
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Is the self-test of the slow down warning lights working? Do read your TR OM for a lot of useful information -- it's not an over-sized phone book, like a modern car, and really has a lot that's good to know.

 

As Steve says, check for lights on start up to make sure that no dodgy previous owner has pulled the light bulbs.

Having said that, the previous owner of my F-car had rewired the instrument panel so the lights came on during startup (even though the sensors were not hooked up). The lights went out as normal after startup, but fortunately I discovered this ticking time bomb before it exploded.

 

I confused myself. Maybe this will help:

Jon, your pic showed the connectors for the O2 sensors. Steve’s comments are correct about the open loop etc.

The bung on your cats as shown here is for the temp probe. The temp probes connect at the location shown in Steve’s pics for the Slow Down ECUs. The O2 bung is a much wider, female thread.

My correction…. The temp probes turn on the overheat light on your dash. As I understand it, they do not talk to the FI unit, they only turn on your overheat dash light.

The O2 sensors provide data for your fuel injection system as Steve points out.

Two independent systems.

Steve…. Jump in if I got it wrong.

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Nothing wrong with that, but the OM gives more practical useful information about how to operate, info about what to expect when operating, etc.. Be warned that the basic TR WSM covers the early euro version TR (F113A engine K-Jet without Lambda injection). For the US version TR (F113A040 engine KE-Jet with Lambda) there is a supplement to Chapter D that has additional pages D61 - D106 -- give a shout if you need that and I can post a link to a pdf copy (and you'd need a copy of the 509/88 US TR wiring diagram).

 

The temp sensor is upper left. O2 bung on lower right. Most of these cats can be mounted with flow direction going either way. Confirm that the temp sensor is downstream.