D4D Exhaust/Turbo problem off 4x4 action

[Hilux Max]

Guys,

a bloke on 4x4 action forum has had a problem with his D4D Hilux....2006 model and I thought I'd share it here and get your opinions and thoughts on it as it has me puzzled.

I'll list the quotes from there from what he said and hopefully someone can help make sense of it.

Hi - Last week my 2006 D4D SR5's engine light came on while i was driving and it lost all power. I pulled over switched it off for a few minutes and restared it again and the light turned off and it was fine. The other day it did it again!
I plugged the scanner into it to see what trouble code it has registered and it has come up with the following code:

P1251 (34) - Turbocharger stepper motor circuit (intermittent)

Has anyone had this problem or know what could be causing this? I have asked around and no one seems to know much about this problem.

No chip, just a 3inch exhaust and snorkel. Its just come out of warranty!

Ok, I replaced the turbo with a brand new one and two days after i installed it, the same error has come up and the car went into limp mode. After I switch it off and restart it, the cars fine. Cant be the turbo! Any ideas what else could be cuasing this?

Finally figured out what was causing the P1251 turbo stepper motor error....
The 3inch exhaust!

I took the Lux to Toyota and they said that the 3inch exhaust is causing the stepper motor to work twice as hard because the boost or pressure would of changed due to the exhaust. I bought the exhaust from the same place you got yours, so its weird that you havent had any problems.

Now this bloke has the same Sterling exhaust I have fitted and I find it funny that his hilux has gone into limp mode over it.....and Toyota is blaming the exhaust system for changing the boost pressure.....I personally dont think the exhaust changes the boost pressure as its computer controlled is it not?

Shane, what are your thoughts mate......just wondering if this might hapen to my bus in the long run?

Cheers

[olcoolone]

The comment sounds like it can for an ill informed unknowledgable person who works at a Toyota dealership (Maybe the lunch boy!).

I like people like that, I like to challenge them on how they can to there conclusion and ask them what data they have to back their claim (been around engineers for to long).

Sure the stepper motor would have a duty cycle but it would be no different if he was towing in hilly areas or in stop start driving, the stepper motor still has to control boost and alter the scroll wheel at different points constantly to maintain peak power at any given engine speed.

[Quinny34]

Wont be either the turbo nor the exhaust, we've got plenty of blokes running them with none of these issues and indeed it sounds identical to my last rig.

We've had at least 1 case of the stepper motor for the turbo on this site causing issues before but I'd have to hunt around for it as it was burried in another thread.

When you turn the car past ACC to ON you can here a ticking noise under the hood, thats the turbo stepper motor....

At a guess, and Shane/Crossport will be the man to speak with, I'd suggest this motor is playing up and or the the sensor for the stepper motor is faulty. It could also be associated with his MAP sensor (Manifold Absolute Pressure) as this is one of the main sensors used to vary the turbo boost. So depending on the MAP pressure it will tell the stepper motor to cut the boost by opening the vanes and letting more gas blow by rather than spin up the turbo..

A professional turbo place would be the better option than the toyo mechanics.

[crosssport]

Max,
A good quality aftermarket exhaust will allow the turbo to spool quicker and I have been told by both manufacturer for humex and steinbauer that as a general rule it will also give a boost gain of 1-2 lbs.
If the cat is removed this can cause boost spiking due to the certain lack of back pressure and flow requirements, which inturn will cause limp mode and engine light to come on. By turning off and restarting it clears limp mode as system is all fine at idle. Haven't heard of this happening personally but have been told about it, some performance chips and exhausts without cat have been known to do this, but never heard of it with the cat fitted.Could be worth checking egr control and soot build up also as this has a lot to do with turbo operation.

Cheers
Shane

[Quinny34]

Just some fyi on how the mechanics of the turbo work...

http://s471.photobucket.com/albums/rr71 ... _Turbo.flv

<a href="http://s471.photobucket.com/albums/rr71/quinny_23/Misc/?action=view&current=VN_Turbo.flv" target="_blank"><img src="http://i471.photobucket.com/albums/rr71/quinny_23/Misc/th_VN_Turbo.jpg" border="0" alt="Photobucket" style="width: 160px;"></a>

(Cant get the darn movie to link properly... let me know if you have issues)

[Hilux Max]

Thanks for your replies guys.....I too found the comments by the toyota mech somewhat off target......

If the exhaust truly was the problem then my hilux would have shown similar symptons ages ago......

Just thought Id share this blokes predicament and get some opinions on it.

[GreenHilux Guy]

Ive got the Taipan 3" exhaust and a DP Chip with a finer (oil) filter. I have limped home more than 30-40 times now but it can happen after a minute in the morning or after hours on the highway. Toyota don't know what it is.

I talked to Kerry at Taipan and they are working a solution. At his suggestion I have fitted a turbo boost gauge to see if it limos when the magic 20psi figure is reached. Sure enough with a a heavy foot and short shifting as soon as it gets to 20 the engine goes straight to limp.

This happens with chipped and non chipped engines as well as new and old exhausts. Taipans theory is a turbo/air/fuel soleind that is a bit twitchy around the 20 psi mark.

Now I just watch the numbers and as soon as it gets close I back off and it hasn't happened in months.

[bansheebuzz]

i have had a few turbo control modules fail, this module directly controls the variable nozzle (via ecu inputs) to control boost pressure, Toyota just point the finger at something thats aftermarket but it really plays no effect on the boost level(as the ecu has control over this) or the load on the stepper motor

[rosco01]

thanks Quinny,
Sorry to swamp this thread...

It took me a while to get the turbo movie to work - but ended up running ok.
Clever bit of stuff this...... it appears to me as if boost in the low (1800) to mid (2500) range is controlled pretty much by the vanes - and they get their demand according to what the chip determines as best from engine revs/load......

I can't see me allowing my little engine getting to 4 grand - I had a fit when it went up to 3 at 110 km/h on cruise control downshifting to 2nd...... was quick to take it out of "cruise".....

Interesting to note that the "boost" seems about half of max at 2500 rpm - and about a quarter at 1800 rpm....

Can anyone answer me how we get 343 Nm @ 1400rpm apparently with so little "boost"?

and - I'm sure a great light will shine - eventually .... but what is the difference between kW and Nm.....
I understand one is power and the other torque - but what relevance does it take form in whilst driving.......?

frats,
Rosco

[crosssport]

and - I'm sure a great light will shine - eventually .... but what is the difference between kW and Nm.....
I understand one is power and the other torque - but what relevance does it take form in whilst driving.......?

Nm..torque is what produces tree stump pulling power

Kw.. Is what gives 10 second quarter mile times

Make sense...Towing, torque is what is needed. The more you have the easier it is to maintain speed and hold gears better.

[1siclux]

With this issue i have installed a 3inch exhaust with no cat only has a muffler at rear the factory boost is 1 bar so 14.7psi right when i take of goes to 14.7 then straight up to 21psi then back down to me this is boost spiking is it due to no back pressure at turbo side would a high flow cat help and restrict it abit

if any one could help

[boxhead55]

Sounds to be like Your turbo vans may be carboned up.
To fix this active test your. Stepper motor open to closed 10 time
This can be done using techstream

[ralphernator]

I had a problem similar to this after my engine rebuild - in the end I found that I hadnt pushed the stepper motor plug on far enough. Sometimes the simplest mistakes can cause the most trouble...

[ekohanggara]

I have a problem with error p1251 after change to free flow muffler 3", i use dastek unichip, any one could help ?