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Hello everyone,

Let me start by saying thank you very much for all of the posts here on the forum, they have been extremely helpful to get my truck in tip-top shape. This is my first truck and I am very excited to be working on it (2003 Tundra SR5 AC 4.7L Auto).

I am currently dealing with getting everything on the truck ready for state inspection so that I can register the truck in my name. I had a CEL for both upstream O2 sensors heater circuits, which I fixed. Both sensors had no continuity of the heater circuit, and both connectors on the engine block side had about 13V on the heater circuits with engine on. So I bought new Denso ones from Amazon (2X Denso #234-4169) and replaced them Friday, reset the CEL light using an OBD2 reader and drove the truck to have it run the Emission Tests for inspection.

After several rounds of driving (over 150miles in 5-50 mile trips), I noticed that all the tests would complete except the Evap System. Since the Heated O2 test completed, as well as the O2 test, and I got no CEL, I assume that was fixed. But now, after every few engine starts, the readiness tests reset all by themselves, and they go back to Incomplete. There are 7 monitors available on my Tundra: 1. Misfire, 2. Fuel System, 3. Components, 4. Catalyst, 5. Evaporative System, 6. O2 Sensor, and 7. O2 Sensor Heater. When the resetting happens, 1-3 always show Complete (since they are updated rather quickly), but 4-7 show Incomplete. I drive it around until they all Complete, again except the Evap System, and this would repeat (no CEL, and 4-7 resetting to Incomplete).

I probably got a couple of times when both the O2 sensor test and the Evap System test were the only two Incomplete tests, and after starting the truck they would all reset to Incomplete. Just to point out that I could notice on the engine rpms at start up when this resetting would happen. Instead of starting at the 1k-1.4k rpm and smoothly going back to idling, the engine would start with 1k-1.4k rpm and quickly go back to low rpms like if it was going to die; but it would not die and it would idle back to the normal rpm after a couple of seconds (I am assuming this "almost dying" would happen because of the air/fuel ratio after ECU reset signal or something).

Is this a problem with my ECU? Or because not all tests complete after a certain mileage, do they all reset to try it again? I do not know what to test to figure this out, so any and all help would be appreciated.

I am keeping track of the Emission Tests using an iDiagnose OBD2 reader connected via bluetooth to a tablet running Torque Pro. And I have double checked that this was the Emission Readiness since DTC clear panel and not the Current Drive Cycle panel, which is not supported by my ECU anyway. I think I have put all relevant information, but if I am missing anything just let me know and I will provide, test whatever I need to.

Thank you in advance for your help!
Leo

 

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It might be a pending code that is setting and then clearing by itself. Use your scan tool and constantly scan for codes and see if you can catch one. Pending codes are stored the first time a two trip code is seen and does not set the CEL. If the problem is seen again the next trip will set the active code and CEL. I would NEVER buy sensors off amazon. Lots of gray market stuff on Amazon of unknown sources like the factory's reject pile and offloaded there because the lack of traceability.
 
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