👍

 

A quick test of your catalytic converters is to drive the vehicle until the engine reaches full operating temperature, stop, leave the engine running, put the transmission in Park, set the parking brake, raise the front of the car, and with an infrared thermometer, measure the temperatures at the inlet and outlet ends of the cats. Measure right on the exhaust pipes and not on any heat shields. The outlet temperatures should be significantly hotter than the inlet temps, ideally 100 degrees Fahrenheit or more. If the outlet temps are the same as, or lower than the inlet temps, the cats are not functioning properly. If your tests at idle are inconclusive, try raising the engine speed to around 2,000 rpm and measure again.

For the other two DTCs, I refer you to Bob's post #3 as a good start.

Cheers,

Don

 

This is quite a saga!

Perform the test Don suggests above in post 102 and report back.

In my experience with the X200, when DTCs P0420 and or P0430 are present, the only way to permanently correct the situation is to replace the catalytic converter(s).

 

So I crawl down there and the upstream pipes are about 200 degrees HOTTER than the downstream ones …
🤔

 

So after reinstalling that awesome MAF Sensor , there’s some occasional noise (mostly when on idle and reverse) from the engine that sounds like I’m tapping on gas (RWWWRWWWRWWW)
🤔

 

I can guarantee this is not always the case as I had this code and replaced my cats with brand new cats and then still got the same codes again shortly after I replaced them.

I read the tech manual that explains the criteria that makes the p0430 p0420 codes appear and it also can happen due to a vacuum leak. And after hunting for the leak for close to a year I found a very minor leak that produced high ltfts. After fixing the leak the codes did not return. So my p0430 p0420 codes were not from bad cats. They were from vacuum leaks

so I will say it again. Find the vacuum leak

 

Also is this a crack?

 

What vacuum leak could cause a cat code? On a 4.2

 

its a sneaky one. I will fire up the laptop in a minute and get you the criteria the car uses to throw the code and youll see but for now, watch this.

 

I think he failed to check the fuel trims - or did I miss that part?

All the things he mentioned would show up in the trims and also leak-hunting is better done looking at the STFTs as you spray.

 

Ok here we go.. hang on bc this gets a little confusing. People immediately think the catalytic converters are bad when they a P0420 or P0430 code because the names of those codes is "cat efficiency below threshold:" or "Cat efficiency" which makes it appear that the code only appears when the cat is not efficient and they assume its because the cat isnt working correctly. But there are things that need to be explained to fully understand the fault.

First off, the code gets set when the cars PCM calculates the "Ratio of the locus of the upstream/downstream HO2S (O2 sensors) during mixture dither" which it does periodically. The PCM counts the locus of the downstream sensors and If the accumulation of the locus of the downstream sensor exceeds 17, it throws the code.

So what does the "locus of the downstream sensor" mean? It means it compares the characteristics of two signals from the upstream and downstream sensors as far as switching frequency, signal length or period and maybe amplitude. this is where it gets a lil foggy.

A little tutorial on O2 sensors and the efficiency test that our cars perform.

Catalytic converters oxidize unburned Hydrocarbons (HC) and Carbon Monoxide (CO) by combining them with oxygen to produce water vapor, and reduce nitrogen oxides to nitrogen and oxygen. When the engine air fuel ratio is lean, the oxygen content of the catalytic converter reaches its maximum value. When the air fuel ratio is rich, the oxygen content is depleted. If the air fuel ratio remains rich for an extended period, the converter may fail to convert the harmful gases. In order for the catalyst to store and release oxygen, the fuel mixture must cycle between ‘lean’ and ‘rich’. During the lean cycle excess oxygen is stored, and is combined with harmful elements during the rich cycle and released. So the output of the O2 sensors bounces up and down like a sine wave. The upstream sensor outputs a small current (< 50uA) centered around 0A as it senses rich and lean pulses and the downstream sensors output a small voltage between 0v and 2v and centered around 0.450v. As you have a small leak, these signals get biased to one side more than the other and the output gets larger as the leak gets bigger.

So back to the code. The Catalyst monitor which sets the P0420 and P0430 codes operates once per trip, and is not a continuous monitor.

So when you start the car, the monitor waits until all entry conditions are met, including the modeled catalyst temperature reaching its threshold. Once all entry conditions are met, the monitor starts to run. Here's the magic- The fuelling is cycled rich and lean (called dither) by approximately 3% to get a reaction at the downstream Oxygen Sensor (O2S). .At the start of the monitor, delay counters operate so that the fuelling is stable when the diagnosis takes place. If the entry conditions then drop out, the monitor result and execution timer are held at the values that they were when the entry conditions dropped out. The next time entry conditions are met the monitor carries on from where it stopped previously. This will happen for a maximum of four attempts, after this, the monitor will reset and the diagnosis restarts.

The monitor runs for a calibratable period of time, after which the monitor results are made. The monitor results are decided by accumulating "the locus of the downstream O2S signal versus the accumulation of the upstream O2S". The more active the downstream sensor, the less oxygen storage capacity the catalyst has, so the higher the locus value.

With a 100,000-mile catalyst, the downstream O2S is not so active, so lower locus values are obtained.

On the Lexus, the upstream sensor output is a sinusoidal signal moving above and below 0A and the catalyst deterioration level is a ratio of the signal lengths (and areas) between rear oxygen sensor and front oxygen sensor. While the vehicle is running under closed loop, the rear sensor switches the signal much slower than the front sensor. This switching frequency becomes greater and the catalyst deterioration level increases with the catalyst deteriorating. Its similar as far as I can tell but ive included it just because their document has good visuals

A judgment is made when the monitor has finished. The judgment made can either be "normal" or "fail". The normal judgment is made if the accumulated count is lower than a calibratable threshold at the judgment point. The failure judgment is made if the accumulated count equals or exceeds the calibratable threshold at the judgment point. On our cars the threshold varies per the model year. Pre 2004 has a threshold of >17. Between 2005 and 2008 the threshold is > 18 and 2008 and later its >13. If a failure judgment is made, then the relevant DTCs are stored within the engine management system.

The problem is with a small leak, you can get these offset biases or noise on the outputs that looks like a triggered change in mixture that make the monitor count a difference when its really just a muted signal or noise or an offset.

And thats not the only thing that can cause this. You need to look for these problems as well:

• Faulty Three-way Catalyst Converter Bank 1
• Exhaust Tube
• Intake Air Leaks
• Faulty Oxygen (O2) Sensor
• Faulty Fuel injector(s)
• Leaking Fuel Injector (s)
• Faulty Spark plugs
• Improper Ignition Timing
• Faulty Engine Control Module (ECM)
• Dirty Air Filter

I know its complex and sounds bizarre but here's some good reference material!

Read pages 27 thru 39 in this document http://www.jagrepair.com/images/Trai...ve%2006_06.pdf

And read https://www.clublexus.com/forums/att...-p0420_430.pdf

And look at this:

 

It would be best to try and solve the VVT issue as that could be driving the fueling problem. And if you can get run time ploys of the O2 sensor outputs it tells you a lot more than just a STFT or LTFT number. see below (these are in the documents I linked above)

 

One last thing,

Click this link and read all about how the VVT system works. Jag Repair Engine management training guide and Training guide B

you will read how the oil pressure is used ONLY to ADVANCE the cam and not retard it. so flushing the oil and changing oil weights will not help you figure out why the camshaft is RETARDED.

You need to understand how the systems work before you try to troubleshoot them.

According to that document, there is a solenoid that will allow the springs in the VVT mechanism to automatically RETARD the cam when the solenoid is UNPOWERED so I would look there. If that solenoid is not working of not getting power, the cam will not advance

While youre at it, heres some more awesome reading for ya Jaguar training guides from Jagrepair