clancy

For what it is worth, the 16805 code, warm up catalyst bank 1 p0421 efficiency below threshold does not make an appearance until the vehicle has been driven or 30+ minutes. Actually it usually takes driving it, shut down, then start and drive for another several minutes. Then it triggers the MIL. If the SAI is the culprit then why does it not trigger quickly once the car is started? My understanding is this SAI only functions on a cold start. So why is the MIL coming on predictably under this pattern of driving? Wouldn't it trigger the MIL quickly upon a cold start? Or, am I putting too much into WHEN the MIL triggers?

Happy Easter and Passover.

jcman

..and also I have ingested your findings.

Let's not ignore other "gray unknown" factors included, so far you have said it will pass and not pass at certain points of monitoring.

So this might suggest an "intermittent event", Yes.

Is the error finding a "permanent one" my thoughts, No.

Then we should see a condition that is not of a pin point result but of the source out side of the problem, diagnostic tree's are the way of my life
and I have learned all by myself as much as I ignored them early on that they lit a light in my head during the trial and tribulation year's of 20yrs plus in my trade of diagnosing problems not too far out-side of this issue.

If you think that you have an issue with the SAI system explore it, then come back and tell us, do this first.

ezveedub

SAI is used during cold engine start, BUT cannot be checked for functionality until the engine is hot with active O2 sensors in closed loop mode. The vehicle will at some point run this diagnostic test on the SAI when the criteria is met and test it to see if the SAI is working properly. That's why the CEL for that code does not come on when the engine is first started.

As for the cat efficiency faults, they are tested once the car has driven at a constant speed with a hot engine in closed loop mode. It usually triggers the CEL after two key cycle test drives. Cats most likely need to be replaced.

clancy

Good info jcman and ezveedub. I will pursue.

SloopJohnB@mac.com

I'm more inclined to believe it's a worn/slow front 02 sensor or a vacuum leak. Old engines, old plastic/rubber vacuum lines.

ezveedub

In general, you should get no response or slow response DTC if the front O2 sensors are bad. In most cases where an O2 sensor is faulty, has no DTC codes for it and is triggering a catalyst fault is when its readings are out of calibration, but yet functioning in a normal pattern. Checking MVB 32 will show if any lean or rich conditions are occurring. Fields 1 & 3 for idle mixture (+5% to -5%) and fields 2 & 4 (+10% to -10%). The closer to zero the values are, means the actual mixture read by the front O2 sensors are to base mapping of the ECM. This is where the ECM adapts the mixture for proper catalyst function. Once you break beyond the normal values listed above, you set a DTC fault in the ECM. Fields 1 & 3 and 2 & 4 should read indentical, UNLESS you have a bad front O2 sensor/wiring or leakage on one bank.

clancy

I went to the generic OBD2 and looked at the oxygen sensors real time trim both long term and short term. Long term B1S1 3.1%, B2S1 3.9%. Both B1S2 & B2 S2 in short term were continuously changing 0.0%, -1.56%, -2.34%, etc. Voltages changing as well. TID 09 time between sensor transitions 0.440, .040, etc.

Group 032 2.1% idle B1S1, 3.9% partial B1S1, 1.1% idle B2S1, 2.3% partial B2S1. Group 033 -2.3% & 0.665 V B1S1, -1.6% & 0.110 V B2S1. Then ran the same test again and got similar but slightly different values on each.

Also, I figured out the SAI pump is fine. I tested it several times. It runs fine, does not sound overly loud or have whining bearings. I mistook it cycling in the engine off test mode for a problem. No problem, just my lack of understanding.

The cat tests, the front sensor tests, the rear sensor test, the aging tests, all the tests in the readiness group continue to show them to be OK.

So would you say it is safe to assume the sensors and cats are fine? I just don't get why I continue to get the 16805 code. I feel like I am going in circles. Could this be the over sensitivity to the difference between the front and back sensors so many people have spoken about? Should I move the rear sensors or put the anti foulers in?

Or, am I just not hearing what you are saying?

Thanks for your patience

jcman

Do you have a leaky flex joint?

ezveedub

I would suggest checking the flex joints also. With the car running, see if its leaking exhaust gases.

If not leaking, based off some of your values. Make sure you have no leaking vacuum hoses (fuel pressure regulator to manifold), PCV hoses, etc. If all is OK, you could try replacing the Bank 1 O2 sensors. Possibly the rear first, since it monitors the precat, then a front if the DTC comes back. Just make sure you don't have an exhaust leak, as you need to fix that first, but if the flex joint is leaking, you will need to get it repaired at exhaust shop or replace the Bank 1 catalyst.

clancy

I will check the flex joint, exhaust overall, and hoses. Thanks