O2 Sensor Connections on an 86TR

Cliff -- The good news is that the 2-pin molded connectors are just a +12V line and a ground line to run the internal heaters in the O2 sensors so those can be interchanged with no bad effects. The bad news is that the single spaded (output) wires are bank dependent. Going by the colors will only work out: 1) if they were right in the first place, and 2) if you were sure that you put the O2 sensor that was in the 1/6 position in your old system in the 1/6 position in your new system.
Do you have a multi-meter? If not, I think there might be a way to sort of wing it (if your TR was running well before the exhaust work), but let me know (I want to minimize my homework!)

(Can you explain why when disconnecting this rat's nest you didn't mark who was hooked to whom? )

 

I too would be interested to know how to tell which side is which. I've always suspected that mine may be crossed at times due to erratic behavior of the motor. I've also wondered how to tell when an O2 sensor is bad. I don't want to cause anyone to work too hard (hint....) but this would be good to know. If there was a reference source where I could look it up I'd appreciate it. Can O2 sensors be tested off the car on some "static" way?

 

Hi Mr. Green,

Unless O-2 sensors fail completely, they tend to lose "responsiveness" over time. Can they be tested? If you had an oscilloscope to attach (in series) to connector during "closed loop" might be able to determine fluctuations/second. Not sure what would consitute "good" versus "bad". Definitely "bad" if return a static voltage (while plugged in; this is normal when running "open loop") I have a thread on FT under "328 exhaust popping" showing pictures of propane torch and voltmeter readings of sensor (bench testing). New Bosch are about $130 with wiring, to splice in runs about $20 less from Importec.com.

HTH,
Carl

 

My 88 TR wiring manual shows the O2 sensor signal going to pin #7, in the large connector, going to the FI ECU. Take the connector off and use an ohm meter between pin #7 and the O2 sensor lead. Try this with both sensors..........the one with continuity, is the proper one. The ECU facing the front of the car, controls the left side of the engine.

My 86/87 TR wiring manual also has the front FI ECU serving the left side of the engine..........also pin #7.

 

BTW: When you look at the large (25-pin) connector, you will notice two rows of contacts........one row has 12 connectors, while the other has 13.

The #7 pin is the 7th connector, counted from either side, of the 13 pin row.

 

Cliff -- Just wanted to confirm what Henry posted:

1) the forward-most injection ECU controls the 7/12 side, and

2) pin #7 at each injection ECU should be connected to the single output wire from that bank's O2 sensor.

(See the schematic on pg 74 of your TR OMs for how to figure out who pin 7 is on the injection ECU connectors -- if it's not labeled/molded directly on the connector body itself.)

I hadn't noticed before, but on the '88 US TR wiring diagram they only give a size ("1"), and no color, for those single (shielded) wires from the loom that go to the O2 sensors -- so can't confirm/deny your "verde" observation.

(Please ignore this if you're already BTDT, but)
If you've not unplugged a TR injection ECU before, the connector sort of "hinges" out in a horizontal plane about a hook on the forward end of the connector (after holding "open" the metal clip at the rearward end of course). I've always had to unplug things in order C13, C12, 1/6 inj. ecu, 7/12 inj.ecu -- i.e., I don't think you can just unplug one of the inj. ECU by itself easily.

Good luck with wrapping up the project...

 

My wiring diagram also gives the O2 wire a #1..........but it adds the following: "Schermo" to it. The S is bold, referring to the color pink? The 86/87 wiring manual only gives the #1. The "Schermo" is stated for BOTH O2 sensors, so it would seem that both are the same color...........right and left bank.

 

"Schermo" I believe translates as "shield" or "shielded" in this case (as in the wire hooked to pin #7 is part of a coax arrangement shielded by an outer braided conductor hooked to pin #8)

 

So neither wire is coded for color. I will just have to take a look at mine...........tomorrow.

 

Thank You Very Much Steve and Henry. This is great information! I will verify my O2 sensors this weekend. Hopefully they will match up with my labels, since I've unhooked them for the engine-out work.

Has anyone had experience with a running TR where the sensors where hooked up opposite? If so...what did it do? How did it run? I can see this easily happening since there is no clear indentification between the left and right sides. Could any damage result from them being swapped? If not, just for giggles, I may just switch connections for a few minutes to see what happens...just for my own reference and curiosity.

I'm now thinking I may want to replace my O2s with new ones just to eliminate that variable.