Clive-D

P0031, P0051, P0057 and P0102 codes on 2008 RX400h

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Hi. My trusty RX400h (2008, 125k) engine light came on this morning half a mile from home, so I went back and parked it.

This afternoon OBD2 reader gave me the error codes in the title.

I noticed recently the engine was cutting in more often when stopped at lights etc so I'd turn off the aircon. Also noticed (ie could feel) the engine cutting out when stopped - not imperceptible as it has been.

Whilst getting the readings, I now notice the engine stops when I turn off climate control and starts up when I turn it on. The engine starts almost as soon as you switch the car on, so I'm fairly sure the issue is as per the codes. The engine sounds rough idling with climate control on and smoother with it off.

My question is... would the P0102 fault trigger the rest to fail or visa versa, or am I looking at replacing all the sensors, which might as well include Bank 1 Sensor 2 which is not showing an error yet.

Attached is a picture of the codes.

How difficult and expensive is it to do the work myself?

Thanks in advance!

IMG_1310.png

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Once the MAF malfunctions all systems downstream will be affected, since the mixture being advised is incorrect.  The engine behaviour you've noticed also indicates an incorrect mixture.  So tackle the MAF first.  O2 sensors don't all go just like that.  The only odd thing about this is if it has just happened overnight.  Normally there is a period when engine and transmission smoothness begins to suffer - I don't know if you've noticed any changes in the last few days/ weeks.

I can't help much with the best course of action - ie whether to try cleaning it first or just replace it.  This would depend on how old is the MAF and what are the norms for MAF age in these engines.

 

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2 hours ago, BachelorDays said:

Once the MAF malfunctions all systems downstream will be affected, since the mixture being advised is incorrect.  The engine behaviour you've noticed also indicates an incorrect mixture.  So tackle the MAF first.  O2 sensors don't all go just like that.  The only odd thing about this is if it has just happened overnight.  Normally there is a period when engine and transmission smoothness begins to suffer - I don't know if you've noticed any changes in the last few days/ weeks.

I can't help much with the best course of action - ie whether to try cleaning it first or just replace it.  This would depend on how old is the MAF and what are the norms for MAF age in these engines.

 

Thanks BachelorDays, that's what I was hoping and seems a good starting point. The MAF will be original, so 10 years and 125k miles, I read on a USA forum that 100-120k is around the time they go if they will. My car is so super smooth and quiet, but I have noticed over the last few weeks when pulled up at traffic lights the engine keeps running a bit longer than it used to and when it stops you can feel a judder, like when the timing or mixture is out, so what you say makes sense.

Just ordered some MAF sensor cleaner from amazon so we will see. Also looked on YouTube and saw various vids on cleaning and error codes. Found this one helpful for the info on error codes...  Cheers

 

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Check the state of your 12v Battery and earth connections to the engine as poor electrical power can cause multiple sensor issues. 

A bad MAF cannot trigger heater circuit errors in the O2 sensors, it could only trigger rich/lean errors from the O2 sensors by incorrectly fuelling the engine.

O2 heater errors cannot trigger MAF errors.

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Thanks Colin, I'll check that. New to the RX which I bought in March. It's been a great car, this is the first issue. It rattles and ticks over lumpy when climate is on, seems ok when climate off. Will check Battery thank you.

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Well aware of that - I'll have to check the history, I think it has been replaced, but I'll have it checked. Thanks again.

 

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Hi Colin - Battery replaced March 2017 by previous owner, just before I bought the car (RAC £125 fitted, gulp!!)

Cleaner arrived today. The sensor was dirty so hopefully I have sorted the problem as it is now nice and clean. I read online the engine light should go out after about 20 miles. Is this correct, or do I need to disconnect the Battery to reset the warning light (not keen to do that as I suspect I'll lose all my Satnav and radio tuning, or is that not the case? Happy to try driving to see if that clears the engine light.

Thanks for your help guys.

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Engine check light normally goes out after 3 engine start/run cycles with no fault detected, doesn't really matter how many miles each trip is as long as it gets up to a reasonable operating temperature each time.

You can disconnect the Battery for 30 seconds however you will need to re-initialise the sunroof/windows/power hatch. You won't lose radio or sat nav presets though. Whatever app you used to read the codes appears to have a clear codes option at the bottom, that will clear the warning light and easier than disconnecting the Battery.

It could of been a temporary glitch but if the warning lights don't go out, or you get the errors again then definitely check the Battery -ve connection, and earth straps going to the engine as it really seemed like an electrical issue.

I doubt cleaning the sensor would stop those faults occurring, and the heater errors are essentially unrelated, but it will likely restore some smoother running and better economy if it was very dirty.

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1 hour ago, Clive-D said:

 

Cleaner arrived today. 

 

Out of interest, what 'cleaner' did you use?

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I recommend just using isopropyl alcohol but others work well.

 

Same procedure as below, MAF just in a different location.

 

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Your code reader should reset the codes.  I'm not too keen on connecting and disconnecting Battery unnecessarily.

I do take ColinBarber's point.  It is a voltage issue if the O2 sensors are giving a heating element issue.  In fact, your engine staying on for longer and coming on more also indicates a possible charge/ electrical issue.

Voltage blips can get a MAF to misbehave as well (and effectively kill it so cleaner won't help).  However, do note that a MAF can indirectly cause voltage issues too - it makes the engine stutter/ hesitate and flood and that may well, in turn, cause the alternator to give a voltage blip.

O2 heater circuit errors on traditional engines are easy to follow since these will normally only happen at initial engine start-up (I think it has a check at 5 seconds).  But where engines are starting and stopping many times they will be more difficult to track.

Let's hope the MAF cleaning works.  Please do tell once you've driven it.

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31 minutes ago, BachelorDays said:

it makes the engine stutter/ hesitate and flood and that may well, in turn, cause the alternator to give a voltage blip.

That would be the case on a traditional engined vehicle, but the 400h doesn't have an alternator - the hybrid batteries and inverter provides 12v once the ignition is on ('Ready' mode).

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59 minutes ago, ColinBarber said:

That would be the case on a traditional engined vehicle, but the 400h doesn't have an alternator - the hybrid batteries and inverter provides 12v once the ignition is on ('Ready' mode).

Thanks for this - it made me look up the way it works.  So the 12V Battery is just to pass control over to the hybrids and the Inverter does the charging.  Of course, the engine provides the power generation for charging the hybrids.  So is it a lumpy engine causing a blip somewhere or is it a blip somewhere causing the lumpy engine?  I hope Clive gets the car back to normal soon.

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@Clive-D It's important to bear in mind that ECU error codes are not direct indicators of an actual specific fault, they are simply the result of a particular error condition occurring which could have many possible causes, sometimes hundreds or even thousands of potential causes. Many people fall into the trap of seeing an "O2 sensor code" (or whatever) and just assume that it's a nice logical simple system and they can simply replace the sensor to correct the issue.

There's some good advice in this thread re cleaning the MAF etc, but if those avenues don't work out don't start throwing parts at it without getting a definitive diagnosis from a garage that knows what they're doing because you'll run out of money before you run out of guesses :)

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13 hours ago, PCM said:

Out of interest, what 'cleaner' did you use?

Liquid Moly Air Flow Sensor Cleaner. £14.95 on amazon. It’s German so thought it would be good quality.  Worked well. 

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21 hours ago, ColinBarber said:

It could of been a temporary glitch but if the warning lights don't go out, or you get the errors again then definitely check the Battery -ve connection, and earth straps going to the engine as it really seemed like an electrical issue.

 

Hi Colin

Drove the car today and had it washed at Tesco 🙂 so it's had more than three starts. Warning light still on. Cleared the codes and engine light came immediately back on and I got the same error codes..

Back home I checked -ve connection which is perfect on any earth point I tried incl the engine.

More worrying is when I collected the car from the hand wash the "Check Hybrid System" warning light was also on. Only a mile home so drove.

Saw a couple of YouTube vids saying to disconnect the MAF sensor when the car is running. If the engine stops the sensor is working, if engine keeps running it is faulty. Mine kept running.

Whilst doing this something nasty sounded under the 12v Battery - like electrical fizzing. Not all the time, but for a few seconds every few seconds. Smells electrical and bad so it's switched off for now. Doubt the hybrid warning can be connected to the MAF sensor issue, can it?

I agree with m4rkw, but I'm tempted to replace the MAF sensor before I get the car towed in to Lexus, but maybe not worth it if they are unrelated. Dreading anything to do with Lexus as I'm not a wealthy man! This is starting to not feel good 😞

Oh yes, and fuel consumption going down noticeably which points to a faulty sensor.

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Get an indy to diagnose it, you could end up replacing a perfectly good OEM MAF sensor with a dodgy aftermarket one and just cause even more problems in addition to the one you have. It sounds like a clear problem so i can’t see it costing more than an hours labour to diagnose.

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6 minutes ago, m4rkw said:

Get an indy to diagnose it, you could end up replacing a perfectly good OEM MAF sensor with a dodgy aftermarket one and just cause even more problems in addition to the one you have. It sounds like a clear problem so i can’t see it costing more than an hours labour to diagnose.

Not sure an indy will know about the hybrid system?

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A toyota specialist should shouldn’t they?

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12 minutes ago, m4rkw said:

A toyota specialist should shouldn’t they?

True - they are next to each other in Guildford! Is it safe to drive or shall I get it trailered in?

 

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I haven’t a clue sorry. Maybe someone else can answer that.

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Btw you might like the podcast “the automotive hour”. Those guys run a garage in Baton Rouge and they’re constantly telling stories of people who’ve come into the shop having spent hundreds of dollars on parts, often in response to error codes, without fixing their problem only to be told it was something silly like a broken wire 🙂 I’ve learnt a lot about cars listening to them.

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Actually you could email the guy from that podcast Louis Altazan, he knows Toyota/Lexus very well and might be able to tell you what’s likely wrong with it and whether it’s safe to drive. go to agcoauto.com and fill in the contact page, he’ll get back to you usually within an hour and answers email about any car problems for free.

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2 hours ago, Clive-D said:

Doubt the hybrid warning can be connected to the MAF sensor issue, can it?

No, that is normally an electrical issue unless there is a problem with the inverter. I'd try another 12v Battery first if you can.

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