Hey guys, per my Ultra-Gauge I am getting this reading (see image). I've looked and and it appears that either my upstream oxygen sensor is dead or my catalytic converter is dead. Does anybody know exactly what this means? I tried testing exhaust pipe temps before and after the cat to determine if the cat is still good, but I don't know what to compare these temps to. Before cat was around 300 F and after was 200 F. Engine was operating at temperature. Should I at least replace the upstream O2 sensor and see what happens? The engine had a bunch of misfiring issues that I have since corrected. 1000 miles after new plugs, wires, coil packs and vacuum leaks plugged. Thanks!

 

I'll bump this for ya. Getting the same one.



My scanner however says this:




I ordered new upstream O2s. No idea if that will fix it. I do worry I somehow swapped my sensor inputs. I just did a motor swap and. Not sure I got em right.

 

Easy to check by keeping one bank disconnected, then see what the code is or real time data. Also could check the wire colors at the ECU side of the connectors vs the wiring diagrams.

 

I'd love to. I can't seem to find the wiring diagrams. I'd buy them if I could find them. I keep getting Advanced EVAP or a D2 diagram. They aren't in the shop manual.

 

Shift, all the diagrams you are likely to ever need can be found in the google drive link in my signature. Help yourself.

 

Holy Crap. Got it now. Thank you.

 

Shifton, I keep a pdf copy on my laptop of the Electrical Troubleshooting Manual. I uploaded it years ago, but don't remember from where. It has all the wiring diagrams with files for each year. For some reason I was thinking you had a 97 D1. The wiring for the 97 shows the solid blue on the right and solid orange on the left. The other three colors are the same on both sides.

 

If your primary O2 sensor is bad, replace it. If your downstream sensors are bad they may need replacing too. Check the voltages.

If you are getting bad catalytic converter warnings, go on youtube and search out how to get downstream O2 sensor from throwing a fault ....or overcoming P0420 warnings. It's very interesting and there are a few different 'fixes' guys have come up with.
One possible 'Fix' for the 'weak cats' check engine light is to wash them out, restoring their operation. The results are inconclusive. Weather washing them out works, some guys say it works others say it doesn't. Guys say to soak in a soapy solution overnight or for a couple days ...then rinse out. It 'might' work on converters which are heavily oil-soaked ...assuming whatever caused the oil contamination was repaired and the catalytic converter internal coatings are still 'good'. Obviously it can't make a difference if the cat's internal ceramic coatings have become damaged or degraded. You could also bite the bullet and replace the catalytic converters ...but that costs quite a bit of money on a D1.

Another ingenious solution people have come up to deal with Catalytic converter warnings include using 'spacers' which stand-off your vehicle's downstream O2 sensors a little bit. Doing so spoofs the computer into getting a more even voltage reading so it thinks it's a 'good' signal. That keeps the CEL off. It's a way of 'tricking' the computer. The stand-off's might or might not pass an emission inspection, but if your goal is to get a 'weak catalytic converter' CEL message off, it's an idea and not expensive. Again, go on youtube and read up on O2 sensor spacers. There's also the resistor/capacitor method too (linked above).
https://www.ebay.com/itm/124721979651?

Still yet another solution, is an electronic-based interface device. There exist certain tiny electronic devices you can plug the vehicle's downstream catalytic converter O2 sensor wire connectors into (eliminates the downstream O2 sensors). The electronic devices provide a computer-happy signal saying "all's good". It's a more expensive solution than those listed above, but if the catalytic converters have been removed, e.g. for racing, off-roading, or whatever, then its a viable method to keep the computer happy and keep away the nuisance check-engine warning. (Note: search ebay).

So, there you have it ...a few different options how to deal with O2 sensor warnings. Obviously your primary O2 sensor is the one that affects engine operation and should be replaced if faulty. The downstream O2's are informative (per gov't regulations) to 'inform' owners/shops/testing agencies when the Cats aren't working (at least the sensor not reading properly). But as I have pointed out there are real-world solutions and work-arounds to deal with it, depending on your specific problem and specific goal.

Best of luck!!

 

Mark thanks for all the good info!

 

I would like to add real quick that when I had my motor out and got everything back together that I bent the tabs on the fly wheel that are the the reluctors for the crank position sensor. If these are bent and contacting the crank position sensor it can throw odd emission codes. Pull off the inspection port and spin the motor and take a look at every tab on there and make sure they are very straight. They are easy to hit with a wrench when bolting down the torque converter. Just a thought and worth looking at if your options dwindle as possibilities are eliminated. I don't remember what code my 97 threw exactly... I'll dig back and find out if you need me to. I posted it here about 3 years ago.