D4D 4.2 Engine Fault Code P1251

[2manyg]

Hi guys, my D4D 4.2 is having problems with intermittent lack of power above 2600-2700 rpm, and it will often go into 'limp home' mode when going up a steep hill, or when accelerating hard.

The engine fault code is P1251, which states ' Turbocharger, engine boost condition - limit exceeded.'

Having seen some excellent guides on this site, I have tried the following so far: spraying a can of 10K into the turbo, filling the vsv with WD40 and shaking and draining, and cleaning the EGR (admittedly this could have been cleaned better as I had no carb cleaner at the time)

Any ideas? The turbo itself seems fine and sounds normal, the pick up until 2600-2700rpm is excellent, and is sometimes ok throughout the rev range.

Reluctant to go to Mr. T as I know they will just say it needs a new turbo.

2005 XT5 D4D

[anchorman]

Welcome to the club.

Check for leaks in the pipe up to the turbo pressure sensor. You could also check that the linkage is free from the vac unit to the turbo variable nozzle.

[igormus]

hi matey

check with flexibility of variable vanes drive on their axises. besides -- check with vacuum attachment with an impulse tube joined to suction /intake manifold. That is what you can do around the turbo. Besides -- before dismantling it for cleaning -- you have to open an EGR upper lid to inspect carbon deposits quantity. The more deposits the more risk to have similar inside the turbo. Do not forget to check with an air filter (engine's) regards/Igor

[2manyg]

Thanks for the tips guys, I'm getting bit thrown by all the terminology!

By turbo pressure sensor do you mean the one next to and slightly above the vsv / vrv? Would air leaks in th epipes be easily detected by a hissing sound, or should I coat them in a liquid and check for bubbles?

And by vac unit and turbo variable nozzle do you mean the actuator linkage between turbo and the actuator that adjust the turbo vanes? Should this move on it's own accord throughout the throttle range?

Thanks again for the help, I'm not afraid to get my hands dirty but working on a turbo is new to me!

[igormus]

i doubt an idle rpm will allow you to hear a hissing sound -- you might to rev the engine and even use a foam to detect holes/leaks;

as to vacuum cylinder (attachment) -- this one is only amplifier that increases a signal from intake vacuum. a linkage is not what do you have to inspect. ok look -- each vane seats on respective own pin called an axis and this pin seats in respective bushing inside the turbo housing. when a gap between a pin and bush becomes less due to carbon deposits -- the vane suffers from lack of full ark movement and a vacuum created by the suction can not over force this carbon resistance/brake. Yes -- you try to push a pedal and over fueling engine but it does not react and not follow yr command. I suggest you can manually try to move a linkage to evaluate how it easy moved. Besides -- you can remove a rubber suction hose and to rotate the shaft impeller to evaluate its rotation / radial / axis gaps.

of course the vanes rotation angle depends on a throttle gap position (i exclude small ark angle subject to poor compression in the cylinder) regards / Igor

[anchorman]

You could try a soap water solution to check for leaks. The layout is here;

Valve layout.pdf

That link from the vac unit to the turbo should be dead free so unbolt the vac unit and work it to check. Now as Igor says, if it is stuck, freeing it will be another story. It could well be bunged up with carbon. One way of avoiding this in the firts place is to stay away from supermarket diesel. Getting it out is another matter. One member managed to get it all free and working again or you could try a tin of BG244 in the diesel tank.

Valve layout.pdf

[2manyg]

Hi guys, thanks again for all your help.

I had another look at the VSV as I read here that it should make a noise if shook. I removed it and applied more WD40 and gave it a violent shake! There is a very quiet small click when shook, I'd estimate the shuttle inside is moving about 1mm at most, is this normal? Should it move more and make a noticeably louder click? If so I guess I need a new VSV?

Turbo, I removed the actuator and tried moving the linkage, it only moved about .50mm then after applying a bit of pressure it moved all the way up and down, but with a 'sticky' point half way. I lubricated the linkage and worked it a few times, I reckon it is 80-90% better but there is still a slight sticky point half way through the travel distance.

I then took it for a test drive, it was still 'hiccuping' and going into limp mode when pushed. However, once the engine had reached temperature it was smooth throughout the rev range, no hiccups, and no cutting out, even when accelerating up steep hills. Does this mean it is cured?

[igormus]

what is the fate of vanes rotation? have you reached all vanes polar points in both directions?

how are they rotated? smoothly or ...... ?

[2manyg]

Hi Igormus, I have not actually removed the turbo and taken it apart so I am not sure what condition the vanes are in. Unfortunately I think removing the turbo is a bit beyond me!

From moving the actuator linkage up and down I would say they are getting their full travel, but there is still a 'sticky' bit, although it is no way near as bad as it was before I lubricated the linkage. The problem seems to have disappeared once the engine has reached full temperature, but is still there when cold. Does anyone know the mechanical reason for this? I would not have thought temperature would effect whether the vanes stick or not.

[anchorman]

A decent garage will have a turbo pressure gauge that you can compare cold and hot pressure.

[igormus]

it is clear visible the turbo needs service -- it is in her best way, but

a good drive on highway would enable gases to burn carbon out from turbo inner side. check with special fuel additive that helps in this job. however please note the turbo is only result but not a reason of your head ache. you still did not reply re EGR condition. i do not touch other possible and presumed issue. regards / Igor

[2manyg]

Hi guys, the initial improvement by lubing up the turbo actuator did not last very long at all.

Today I had the SCV valves replaced, there is a definite improvement but the car still hesitates from 2500rpm. My question is this, would the SCV replacement see an immediate improvement, or will I have to put a few miles in to see the results?

Igor- I did clean the EGR, but not with proper degreaser / carb cleaner, so I'm not sure how effective it was.

i still can't get the VSV to make a noise when shook, should I look at replacing this next?

The fuel filter was replaced by Toyota recently (assuming they changed it as invoiced)

Thanks again for all the help!

[anchorman]

If the SCVs are at fault it will work immediately. However, usually the SCVs give P0627 DTC. Take the pipes off the VSV and join them up so it is piped direct - see how that goes.

[DN04]

Hi,

I had this problem with my (new to me in June 2012) xt3 04 plate Rav D-4D from about Oct 2012 onward. I used a lot of advice from this forum on how to perform some of the things I list below (thanks to the great guys who post how to guides), and spent nearly 5 months trying to solve the problem.

The overboost first occured shortly after I piled through an unexpectedly deep puddle across the road at about 30-40 mph, so I was always suspicious it should be a simple fix related to water in electrics somewhere.

I cleaned the MAF (simple, use electrical contact cleaner spray or the more expensive branded MAF cleaners) - no change. I removed and cleaned the EGR vavle (using carb cleaner and guide on this forum) - no effect (and don't overtighten the top screws, they break quite easily!), I changed all the turbo vaccum pipes - no improvement.

In frustration, I bought a code reader from eBay (less than £20, the reader is cheap, its the quality of the software that matters!) - although you get quite limited data from the older vehicles like mine, it reported P1251 (error in turbo actuation) and intermittantly another code related to a fuel pump open circuit. It also allows you to clear the codes so you can see when the fault next occurs. I found the freeze frame data they store wasn't really much use though.

Toyota told me to replace the turbo (my wife works for Toyota, and even at mate's rates that could easily cost a fortune - around a grand to buy a remanufactured turbo supplied by Toyota).

I also tried a Cat cleaner (no improvement) and redex (no noticeable change) in the fuel tank. At this point a friend found an independent diesel engine expert, who spent a couple of hours looking at the car. He went away and consulted friends in the trade and turbo manufacturers, but he eventually recommended I fit a second hand turbo - told me to do it myself (too scary though!).

Instead, as a last desperate attempt, I put in some (Forte) Turbo cleaner (rather more concentrated than they recommended!) in the fuel tank (bought from Amazon), plus I wire brushed the actuator arm on the turbo where it goes into the housing (bought some small wire brushes from eBay for a few pounds, and reduced their width using a circular saw!), with plenty of WD40, and then lubed it up with high temperature (copper) grease. Its a bit of effort to get in there, but removing the top part of the actuator (looks a bit like a UFO bolted to the turbo body) allowed access (just about). At the same time I thought about replacing the two SCVs (using instructions on this forum) on the fuel pump ("only" a £100 or so each!!), but instead I took the connectors off and sprayed in WD40 and used a steel brush to gently clean the contacts before refitting.

That was in early Jan 2013. It is now mid April 2013 and I've not had a single recurrence of the P1251 or the fuel pump open circuit code (P0627), which I was previously getting everytime I put my foot down less than gently (even had to drive back from Wales at one point doing < 30 mpg, with a very noticeable lack of power and a tendancy to power surge - not an experience I'd recommend).

I don't know if the additive cleaned the variable vanes or whether it was the SCV(s) misbehaving and confusing the ECU or whether it was the actuator arm on the turbo not functioning, but I spent less than £100 (but a lot of time!) fixing the problem, rather than spending £2k-£3k replacing the turbo which may not have fixed the problem anyway.

So although you may not have the same problem as me, I'd be very dubious if advised to replace the turbo for a P1251 error code.

Best of luck people!

[Big Kev]

Stonking first post, Ian.....welcome t'cloob......

[anchorman]

Good stuff Ian and welcome to the club.

It is a good post but you broke the law in terms of diagnostics by fixing 2 things at once. As you were getting P0627, was the turbo fault a red herring?

[Windinherhair]

You could try a soap water solution to check for leaks. The layout is here;

Valve layout.pdf

That link from the vac unit to the turbo should be dead free so unbolt the vac unit and work it to check. Now as Igor says, if it is stuck, freeing it will be another story. It could well be bunged up with carbon. One way of avoiding this in the firts place is to stay away from supermarket diesel. Getting it out is another matter. One member managed to get it all free and working again or you could try a tin of BG244 in the diesel tank.

Hi folks.

Our Rav went into limp mode with EML coming on whilst on a long, wet, cold drive up north on Sunday.

It happened on a long curving hill above Tyndrum.

We checked it there and then with the diagnostics reader (always have it in the boot after previous issues). The fault code is P1251.

Anyway, we cleared the code/light and continued home (70 miles) to see if it would recur. It didn't. No issues whatsoever.

I'm going to take a look at the hoses and the linkage you speak of.

At the risk of sounding a bit thick, I see the hoses are marked but, where is this linkage in the diagram?

The first thing my brother mentioned the other day when I mentioned it to him, was to replace the vacuum hoses. I think he had a similar problem with a diesel in the past. He said just to buy a length from a DIY store. Would this suit? Or is there a motoring grade hose? I had a wee quick look online and saw the hose being available for the model after mine. Is it readily available for the 4.2 2.0 D4D?

I have also just ordered some Forté Diesel Treatment and also the Forté Turbo Cleaner...won't do any harm.

Thanks in advance...

[Jonathan T]

Hi I've just signed up to tell you folks how this forum helped me find a £7 solution to a £1650 problem while on holiday in Switzerland a couple of weeks ago!

I have a 2002 Previa with a 2 litre D4D engine, with around 140,000 miles on the clock. At the end of a long drive through France and up into the Swiss mountains, the engine management light came on. There were no noticeable symptoms until we were climbing a steep hill and I felt a momentary loss of power. However, we reached the holiday flat, and for several days the warning light stayed off, until we went back on the motorway and it came on again; I did continue to feel occasional losses of power.

I took the vehicle to a Toyota dealer, for a diagnostic test. It showed a P076 code, indicating a pressure failure in the fuel pump. I had hoped it might be the catalytic convertor (the only other time I had the engine management light come on) or something benign like that, but this made more sense given the symptoms of occasional power loss.

My worry was that this could lead to a full breakdown on the way back to UK, and I really didn't want to end up stranded on a French motorway, with wife and 5 kids in the car. The Swiss garage said that if I wanted to be on the safe side I had better change the fuel pump - which would cost £1650 for a reconditioned unit. I phoned a couple of Toyota dealers in England, who both said it's very rare to replace the pump on the D4D engine.

So I Googled some more, and found this thread, and a couple of others, where I learned about the SCV valve problem, and began to put two and two together: the loss of power only occurred on higher revs, or when the engine was under a lot of strain, and I had filled up with French supermarket fuel (notoriously dirty apparently). So I concluded that the most likely cause of the problem was that the SCVs were sticking.

Consequently I followed the advice of other users and spent £7 on a diesel injector treatment product, which I poured into the half full tank of fuel. I drove a couple of days like that, including on the Swiss motorway, and the management light stayed off! Then I filled up for the return journey with Total Excellium diesel, which I read is one of the best for cleaning the whole fuel system.

Needless to say, I drove non-stop across France, with no more warning lights or power loss! Wonderful! It's a great feeling to have saved £1638 pounds, and to have fixed the problem myself through a bit of online research!

I'll copy this onto another thread which helped me too... Thanks ToyotaOwnersClub.com!

[Avalon]

Change the fuel filter if you suspect crap fuel, it's an easy job and cheap. I changed the filter on my Rav recently and the crap that came out and state of the filter element was worse than expected. In my case I ran some BP Ultimate through which has 5x the detergent of the regular stuff so I suspect it made the situation worse by flushing through some of the crap that had built up over the last 97k.

[Issi786]

Hey guys. I have a p1251 dtc on a 2012 fortuner 3 d4d. It's very consistent. If I floor the car even while in park it will go into limp mode at around 4500 rpm or if I'm driving and I floor it n it kicks down hard it will go into limp mode guaranteed. It does not miss it. But if I Rev it gradually no limp mode. As long as u are not hard on the gas the car drives very well. 

I have tried a lot to resolve this issue and all has failed :
1) recond the turbo from the car
2) checked egr and intake and it was clean
3) swapped step motor from my hilux
4) swapped maf and map from my hilux
5) swapped turbo drive from another fortuner
6) fitted a whole other turbo with new step motor supposedly better calibrated(not!! Just cond cos I was desperate ) 
7) tried another turbo drive
8) had it by a very good auto lec to check
9) another accelerator peddle 
10) lastly another ecu. Had it cloned and still the same problem. 

Now after a lot of research and testing I see that my map sensor reading seems to be the problem. It's not the map sensor or the wiring. It's the ecu. 

With the ignition on and engine off any map reading should be around 85kpa(atmospheric pressure) in my area . And it is so on my hilux. But the fortuner reads around 185kpa. Even when the engine is running it will also be in the 185kpa region. I think that's where my overboosting issue is coming from. 

It's both the original ecu and the second hand cloned ecu that give high map reading. If I plug the ecu into the hilux an turn ignition to on position the hilux also reads 185kpa as map reading. So the issue is definitely on the ecu. 

Could it be that the fault was copied while cloning was taking place?

Secondly do u guys think the the map sensor reading would cause my p1251 dtc?

Please take note that both pictures are with ignition on and engine off. Look at the atmospheric pressure and the map sensor reading. They should be the same

Any assistance would be appreciated.