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I could be wrong and I don't have experience with OBD2 monitoring but I think you may need to buy a new Denso 4-wire heated O2 sensor for your #2 catalytic convertor if you have an SC300. All California Emission models from 1992-2000 have them and all Federal Emission models from 1996-2000 have them.
The O2 sensor in this location does not directly influence the engine's A/F ratio or other parameters in any way. What it's there for is to monitor the efficiency of the #2 catalytic convertor AFTER the primary catalytic convertor which has two 4-wire heated Denso O2 sensors monitoring just before it on SC300's... and those two front O2 sensors are the ones that actually influence the ECU's A/F control of the engine along with the MAF and other sensors.
OBD1 and OBD2 differences aside, the basic monitoring and A/F control of the 2JZ-GE engines are mostly the same for all model years other than all CA Emission and 1996+ Federal Emission cars getting a bit more sophisticated monitoring hardware (mostly in the number of O2 sensors and type of O2 sensors).
Now that you've mentioned this, there's an exhaust leak before the 3rd O2 sensor, so I wonder if that's why it's not completing. Maybe the sensor is good as no CELs
If you have a CEL code 71 (EGR Malfunction, Obstruction or EGR component failure) then I would recommend doing a diagnosis of the following:
--Check ALL the vacuum hoses throughout the EGR system to make sure none are leaking, broken or torn. This can be tedious. Generally the go-to replacement hose will be a spool of Gates #27042 hose which pretty closely matches the OEM original hoses of this size and Inner Diameter.
--Do an electrical test of the EGR VSV with a simple electrical multimeter, alligator clip wires and your car's 12V battery. You want to make sure that the solenoid consistently clicks when +12V is applied and releases when +12V is removed. The SC300/400 and Supra MKIV TSRM show which terminal pins on the VSV are positive and negative. The next thing you want to do is make sure it can hold and release vacuum pressure accurately with no leaks. Use a MityVac testing tool for this which can be switched between vacuum and positive pressure modes. EGR VSVs for these 92-97 engines are no longer available brand new so it's important to verify the function of yours or any used EGR VSV that you may pick up from eBay or other sources if it needs replacing.
--The EGR valve should be removed and cleaned, then tested with your MityVac tool to ensure that its diaphragm is working correctly with no leaks. Again, the SC300 and Supra MKIV TSRMs cover this test. These should still be available right now if it does turn out that it needs replacing.
--The EGR Vacuum Modulator should also be tested to verify normal function as per the TSRM. If it won't hold pressure in the correct ports and blow through pressure through other correct ports then it would need to be replaced with a new or known good one.
--The EGR metal pipe going from the EGR valve to the cylinder head might also need cleaning to remove clogging from too much carbon buildup.
--Finally there is one more part of your EGR system that should be checked and likely cleaned and that is your "Y" intake manifold/plenum on the top of the engine. Some 92-97 2JZ-GE engines throw a CEL 71 for EGR malfunction due to the internal passages of this part being clogged up with carbon so badly that there is no EGR flow any longer.
For this, amazingly, Toyota has no TSRM procedure to show how they want you to clean it. Instead they seem to have wanted you to just replace the whole manifold part with a brand new one... officially. However the engineers DID conveniently put freeze plug capped passages into this manifold that make it possible to thoroughly clean out these clogged EGR passages.
I had to go through all of this a few years ago to fully diagnose my EGR system on my 1993 SC300 and I ended up doing a couple of writeups on the procedure to clean the Y-manifold to make it flow the EGR gasses smoothly again.
See here and read both thread links. I guess I should combine them together into one thread soon.
I hope this may help you get rid of the CEL 71 EGR code at least. And also yo may be onto something with your exhaust leak under the car near the #2 catalytic convertor. Get that fixed and also check the health of the 4-wire O2 sensor in that location. If it's worn out get a new Denso aftermarket sensor to replace it.
Thank you for the information, but there are no CELs. None pending either.
Today I had the exhaust leak fixed before the 3rd sensor. I also checked the EGR and applied vacuum and the engine idle became rough so I know the valve is at least working.
EGR and catalyst monitors still won't complete. Smog due in 1 day.
Replaced downstream O2 and fixed exhaust leak .
I've been watching the O2 voltages on OBD app and sensor 1 seems a bit lazy compared to 2. Downstream fluctuating between 0.3 and 0.6v pretty frequently so wonder if cat is bad after being replaced 4 years ago (Magnaflow CA spec).
Thermostat seemed lazy so I had that replaced today (coolant may not have been getting to operating temperature for the check)
It is possible that your Magnaflow downstream cat is not working at its most efficient any longer despite being only 4 years old. If the O2 sensors and plugs were not at their best for a while this could have shortened its life a bit. Compared to OEM cats the aftermarket ones aren't quite as good even though they will work well at the onset of their use.
Is it possible that you can get a local exhaust shop to install a new one for you tomorrow? I know that's not a cheap expense at all. If you've tried everything else at this point it might be your only remaining option. Similarly you want to be sure your primary cat is also in good shape but if it's still OEM I'd keep it (the #1 cat) in there as long as you can until you are certain it has worn out.
I had to diagnose a lot of smog related issues myself in 2016 with my SC300 and after doing everything else I did end up needing to replace one of my cats in order to pass. I got my smog test done but barely in the nick of time after all the diagnosis and repairs.
Using an inexpensive laser heat measuring tool you can also read the inlet and outlet temperatures of both catalytic convertors to determine if one of them is clogged up at this point.
Wow, think I this might be the cause of the problem. LOL
Last year the crank pulley had a broken tooth so I had to replace that and did a new timing belt.
Jumped TE1 and E1 to set timing and off I went...and went...and went for the next 15 months. With TE1 and E1 still jumped! I totally forgot about it.
I was researching this issue literally having gone though almost 50+ sites/pages/forums/documents and stumbled on this - the guy had the same issue on a Toyota.
I am very glad for you that it was really just a simple fix not involving a pricey new catalytic convertor (and honestly I'd keep an OEM convertor for as long as you possibly can since they last so much longer than aftermarket cats).
I've had plenty of these kinds of "forgot to put it back" or "forgot to remove it" or "forgot to plug it back in" moments to getting my SC sorted as well. It happens to all of us! It especially happens when knee-deep into a lot of work and/or heavy diagnosis.
Now I hope you can get your smog tomorrow and get your new tags soon! Just keep a photocopy of the smog test form with you in the glove box and a copy of your online registration renewal receipt just in case you need it to prove that your new tags *are* in fact in the mail!
08-29-22, 04:56 PM
-RESOLVED - 97 SC - smog - EGR / Catalyst monitor OBD failing
