Why is the ECU So Outdated?

[eric_rosenwald]

I'm having problems diagnosing a P0420 code on a 2000 (3rd Gen.). I have another thread going on that. I'm learning a lot about what different codes mean, and the fuel system in general.

I've come to the conclusion that the code system is completely outdated and needs to be modernized. There's no excuse for such a primitive system. It's too mysterious.

So...

A P0171 could, among other things be due to “A/F sensor (bank 1 sensor 1)." But a "A/F sensor (bank 1 sensor 1)" situation could also be the reason for my P0420. If it’s truly a problem with “A/F sensor (bank 1 sensor 1),” shouldn’t it say that definitively?.

I understand that engine problems are often complicated and interconnected. But you need to have an equally complicated diagnostic computer system to analyze the engine. These things need to store more engine data, process it with more sophisticated computers that avoid basic logical inconsistencies. These codes and the problems they indicate need to be more mutually exclusive. The codes just don't reflect the interconnectedness and feedback loops involved in a system as complex as a car.

Race car engineers, UPS, Rolls Royce (in their jet engines) use modern software and high-performance computers. There's no reason there can't at least be a modest update to the stone-age diagnostic code system for all current cars. I know it's always risky implementing new technology, and it's good to be conservative in the interest of safety... But there comes a point where you have to risk a little bit. It's worth it. Computer components and software are cheaper by the day.

The ECU uses lookup tables in its analysis... It needs to use machine learning instead!

 

[Doc2012]

P0171:
A code P0171 may mean that one or more of the following has happened:

•The MAF (Mass Air Flow) Sensor is dirty or faulty
Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
•There could be a vacuum leak downstream of the MAF sensor
•Possible cracked vacuum or PCV line/connection
•Faulty or stuck open PCV valve
•Failed or faulty oxygen sensor (bank 1, sensor 1)
•Sticking/plugged or failed fuel injector
•Low fuel pressure (possible plugged/dirty fuel filter!)
•Exhaust leak between engine and first oxygen sensor


P0420:

•Leaded fuel was used where unleaded was called for
•A damaged or failed oxygen sensor (HO2S)
•Downstream oxygen sensor (HO2S) wiring damaged or connected improperly
•The engine coolant temperature sensor is not working properly
•Damaged or leaking exhaust manifold / catalytic converter / muffler / exhaust pipe
•Retarded spark timing
•The oxygen sensors in front and behind the converter are reporting too similar of readings
•Leaking fuel injector or high fuel pressure
•Cylinder misfire
•Oil contamination


If you have both of these codes, go through each one and see what happens. If they come back, go to the next one.

Clear them, and see which comes back first.

I chased around a 420 for months before I found out that the harness I got was the wrong one.

Wrong parts will also cause CELs.

 

[BlackWorksInc]

I would recommend that you read up on Catalytic Converters and how they are tested via OBDII systems. I wrote a decent post on it in a thread I made for the 4th Gen Section:

http://www.toyota-4runner.org/4th-gen-t4rs/132953-toolbox-how-use.html#post1272379

The code system is not at fault, it is simply the way Catalytic Converters are tested from an OBDII standpoint and how they function. The variability in diagnostic criteria is due to a multitude of issues that can cause failures in PIDs that can be interpreted as a Catalyst failure and are limitations caused by the way modern vehicles utilize O2 and AFR sensors in this testing; as well as how OBDII guidelines are set by the government. Rolls Royce, Ferarri, and others are not exempt from this and modern racing teams don't care about emissions.