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Hi, I got recently error code P0420 and P0430 in the same time. The MIL was on. I cleared the code and after 300 miles it comes again. I drove approx 100 miles and the MIL goes off itself.

Any ideas what is wrong? I read that it can be catalyst converter which is bad option. The car is 126K miles now.

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I admit that I haven't watched this video myself but it should hopefully help you. If it doesn't, there are plenty more that should.

 

 

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Thanks.

I just checked the code which goes off itself and it was P0430 (previously P0420 and P0430).

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For both banks to come on around the same time would indicate to me that it probably isn't a cat issue. Possibly an issue with the intake system, a dirty MAF sensor or vacuum leak for example. Worth getting the an OBDII system connected to check out the operation of other sensors and the short & long term fuel trims which may indicate a problem.

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Could someone explain me where are located the banks? Is the O2 sensor bank 1 and 2 located after cat? 

I checked OBDII readings. As explained on the video the bad cat, the waves on O2 sensor 2 should be similar to A/F sensor 1 but I have a question. If I press the accelerate pedal then the O2 sensor 2 (after cat) should change or should it have the same level?

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Sensor 1 is upstream, before cats, and sensor 2 is downstream, after cats.

Bank refers to which side of the engine, for the 400h B1 is nearest the windscreen:

5ad1e0709aab0_ScreenShot2018-04-14at12_04_29.png.9b175f5a0b13b8abc80666d6be56855c.png

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Hi,

I noticed that both codes P0420 & P0430 appears (in the same time) more frequently than few months ago. It happens when system is in Closed Loop (warmed) but not enough (just 5 mins) drive on A road. When the car is fully warmed (drove 15 miles) I cleared the codes and when the engine is still warm enough (driving a lot) then codes doesn't appears but when I allow the engine to cool down, the next time the engine is warm the codes appears.

I cleared the MAF sensor already, changed air filter. I also read the O2 sensors readings but voltages jumping a lot from 0.1 V to 0.8 volts. Other readings seems to be ok such fuel trims (Short -2.6 and Long 0.7). I also checked A/F tests (rich and lean tests) and the delay is avarage 1.5 sec it seems that the cats are still working ok. There are no misfires.

It's strange that the possibility faulty cats started exactly the same time. Next step will be checking the exhaust leaks but it also strange that there could be leak in both banks. Also, I had few trips (each over 1200 miles) on German motorways driving over 80 miles per hour and no sign of overheating or coolant leaks, changes in engine oil level. I guess, if there will be any problem with intake manifold then could be overheating or coolant leaks??

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It is possible for an exhaust leak after the sensors to cause this error as the engine can force in air back up to the sensor. Definitely look at the Y joint where the two banks join.

Otherwise if there isn't a leak it may be that the MAF sensor just isn't working that well, or that both upstream A/F sensors are now lazy with age (unlikely).

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Thanks, I will look at the Y joint and later A/F sensors but as you mentioned it's unlikely that both A/F sensors are faulty at the same time.

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Today in a garage someone made a visual inspection of the exhaust and said that everything is alright. No exhaust leaks. One more thing to check is MAF. It's a simple device I cleaned it already. I'm going to check it using multimeter but when driving the car I can't see any issues and I doubt it's a MAF (errors could appear if it's faulty). 

Also, I doubt two o2 sensors failed at the same time.

I would avoid use o2 spacers because I prefer to find the real source of the problem but in this case, is the solution. Maybe there is an issue in the intake manifold. 

Forgot to add that I had an emission check and it was alright. 

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5 minutes ago, Madartsoft said:

Forgot to add that I had an emission check and it was alright.

I thought hybrids were exempt from MOT emissions testing because the engine can't be revved, so if that's correct I'm not sure how valid your test will be?

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Yes, hybrids are exempt from emission test but I checked also independently the emission and they checked it when I pressed the accelerator (the engine then revs).

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16 hours ago, Madartsoft said:

One more thing to check is MAF. It's a simple device I cleaned it already.

Did you clean both wires? You cannot really test it with a meter, and as you say it won't be 'faulty' as you would get MAF error codes. It needs to be something on the intake side though, if it isn't an exhaust leak, to cause both banks to have an issue - air leak, poor metering etc.

 

 

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Hi, 

I replaced the MAF and still, the same issues P0420 and P0430 as pending now. I also noticed one more thing. I have Long Fuel Trim +10.8 on both banks. I wanted to replace two rear O2 sensors but decided not to do this as ColinBarber suggested it must be something like a leak somewhere. Is there any good method to check the intake leak??

Also, I don't know if it's important. I attached scan tool and on idle (when batteries are charging) the idle is about 1000 rpm. Is it not too high?

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If you have changed the MAF then you want to reset the ECU by disconnecting the Battery to make it learn the long term trims faster than normal.

A spray bottle with soapy water will help find air leaks - spray over the vacuum pipes / throttle body etc. and listen for a change in idle speed/sound. If you have the vehicle in Park, press the accelerator to get the engine to run and shift the transmission to Neutral which should keep the engine running, otherwise google rx400h inspection mode which will keep the engine running.

Idle speed of around 1000 rpm is correct, it helps with charging the batteries.

 

P0420 and P0430 is almost never the result of a faulty downstream sensor - it is working correctly to detect the efficiency problem. If it goes faulty then either another error code is produced or efficiency issues go unnoticed.

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I made readings and tests again today. It seems that all codes disappeared, I made over 130 miles. Also, I noticed fuel consumption improves from 28 to 32 mpg (I tested the usual trip). Now the Long fuel trim shows -20 which means that the PCM removes the fuel. Thanks ColinBarber, probably the PCM is learning and the values are so high. I'm going to disconnect the Battery but it should learn also without this step I guess.

Before changing the MAF the error code appeared after 10 miles drive but now it's over 130 and no codes (no pending codes) ! 

I'm guessing disconnecting the Battery will clear all settings.

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After drove over 200 miles. The P0420/P0430 is back! It's not often as in a past but again I see the codes. Car runs smoothly but even after 200 miles the LTFT shows -18.8 on both banks at idle and -9 when driving quite fast. I think is to check fuel pump pressure but I had not this issue with old MAF.

The new MAF sensor is China cheap replacement £21 maybe it's something wrong with the MAF.

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Hi. My only experience with MAF''s is from when I had a MG ZT diesel. I fitted a black box with the suggested pieburhg MAF unit. My car didn't like the MAF so I put a new original BMW unit in. Car worked superbly. 

Anything to do with a MAF unit the only response is to replace with Original Equipment. Yes they can be expensive But work out cheaper in the long run.

Looks to me that cheap Chinese copy has worn out already. Bin that cheap unit as that's where it belongs. 

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