Hey all,

My 98 D1 O2 sensors have the following color wires. Anyone know which ones are the 'heater' wires ...and which is the signal positive?

Black
White
Red
Yellow

Thank!

 

The best I can offer is to go to the google drive link in my sig. Find the D1 section and look for the electrical troubleshooting manual etlj970x.pdf. Section A3 pages 6-7 will show you the diagram from the connector to the ECU/pwer/ground/etc

Help yourself to any and all documents in that link/drive.

 

Red/white are heaters, black/yellow are signal, I think yellow is positive. But you should know these are variable resistance titania type sensors (not zirconia), so the voltage source is the ECU, then it converts to the voltage signal we see on the OBD reader. I found a pretty good paper at Tomco Techtips. I run my 96 with the downstream sensors disconnected.

 

Thank you. Very interesting. I assume you're getting a CEL code for downstream cats out of spec?? I was considering adding a resistor/capacitor in the wiring of the rear O2's to get the CEL off. No smog inspections in our area. Is there another/better way? It didn't look like there'd be much room for 'spacers'.

 

Yes the CEL is lit, but it was anyway due to cats inefficiency. So I was looking for a way to eliminate the downstream sensors and clear the codes. I also swapped the y pipe with one that isn't tapped for downstream sensors.

I tried a simple resistor (80 K ohm) to get the OBD reading at about 0.45 V, but the ECU is smart enough to recognize that trick, and throws a different code. For the capacitor to work, you still need downstream O2 sensors in good working order. The circuit is a voltage divider, black is a regulated voltage from the ECU near 5 volts. The voltage read at the sensor is converted in the ECU to read from about 0.1 to 1.1 V as the fuel trim is modulated, but those are not the voltages you see right at the sensor. My experience was that the truck seemed to run better with the downstream sensors disconnected vs trying to fool the ECU.

I also read a post on this forum that the engine gets good performance and better gas mileage with the upstream sensors disconnected, but I haven't tried that myself.

 

They make Lambda emulators too ..but cost a bit of money. You probably looked into them already I assume, judging by your research. Do you remember what value capacitor you used? Did you try the 'spacers'? IDK if there's room under there for spacers.

 

I replaced my O2 sensors. Then started to get the CEL. I was going to reinstall them. Maybe next spring.. see if they go away. One issue is when these vehicles develop a coolant leak, that can affect the cats. So it might not be the new sensors, it might be that my cats are too far gone.

 

I didn't try capacitors or spacers. But I did try running a gallon of mineral spirits in a tankful of gas. The concept is to increase the heat in the cats to burn off impurities. There are commercial products available for that purpose too. What codes are you getting? I really struggled with mine and finally figured out I had a bad upstream sensor.

 

Thanks for the info. I'm getting the typical 'weak downstream cats' code. I don't recall now the exact code at the moment. My O2 lights have been on for a while too. I might try the spacer first ...if they'll fit under there, then the capacitor trick after that. I really couldn't find a cat spacer for the O2 sensor thread size of the Disco 1. I'll fab up a couple and see if they work. If not, try the capacitor/resistor trick. I agree, it's an annoyance. If I can get it off w/o too much effort, worth a shot ..for me.

 

IIRC these will fit

linked to incorrect part... my bad.