Electronic Actuator Stepper Motor Information
Stepper Motor and Turbochargers
Electronic Stepper Motors (sometimes called Electronic Actuators) on turbochargers move the vanes inside a VNT (Variable Nozzle Technology) turbo.
The variable vanes do much the same job as a dump valve on a standard pneumatic actuated turbo.
That is, they allow boost and release of gasses via vane movement facilitated by nozzle ring movement that is actuated by the stepper motor.
We supply both Stepper Motors and Turbochargers to the market.
They are sold as separate units to allow the purchase of either part depending on the problem they are purchased to fix.
As such we supply by default all turbochargers and stepper motors as separate parts.
We offer some deals where the turbocharger and stepper motor are sold together at a discount.
Where this is the case, to facilitate ease of transport, the stepper motor will be included separately in the box with the turbocharger.
For installation, 3 bolts off the old stepper motor are usually used to secure the new stepper to the new turbo.
Additionally, the actuator arm is attached via a clip to the stepper and the other end of the arm via a clip to the lever that actuates (moves) the vanes inside the turbo.
The same applies where a stepper only has been supplied.
Here the new stepper will just be bolted to the existing (old) turbocharger unit.
In each case above, it is more common that once the stepper unit is attached to the turbo, it should work immediately with very little adjustment.
In some cases, a ‘calibration’ may be required.
Typical cases where calibration is likely required include (but not limited to):
A fault code relating to stepper motor that persists once code has been cleared even after the new stepper / turbo has been installed.
An example code would be: P0047 which relates to stepper motor, and may indicate low voltage or an out of range boost pressure detected.
Or cases where insufficient boost has been attained or general overboost fault codes are thrown by the ECU (as above code and including cases where the vehicle goes into ‘limp’ mode).
Because of the general nature of most fault codes, they can seem to emulate the same issue as the original that called for replacement of that part.
But the general nature of codes usually lumps 2 or more different issues under the same fault code.
An example would be a stepper motor that is actually faulty, throwing same fault code as a stepper motor that is not faulty, but just requires some calibration.
Another example is where the problem exists outside of the turbo/stepper system and in the ECU unit that controls the stepper or even the main vehicle ECU, or other components of exhaust or air intake system.
Stepper Motor Calibration
Where mechanical calibration only is required, the essence is as follows:
The stepper motor should be allowed to create the correct range of movement to actuate the vanes to give a correct amount of boost across the rev range, without producing over-boost or under-boost.
This is usually facilitated by adjustment of the small stopper screw on the turbo next to the lever that actuates the vanes, whilst testing flow and boost.
An extreme circumstance can occur where correct movement range cannot be attained via stopper screw (if screw length is at max or min length and stepper still requires further movement).
In such cases, a compressor housing re-alignment can be done via slight loosening of the bolts under the compressor housing, allowing a change in orientation between the angle of the housing and rest of the turbo, thereby allowing correct range of actuator movement.
The exception to the typical case where the stepper requires no calibration is for the Toyota Hiace Van.
With these vehicles, it is far more common for calibration to be required.
In addition, where the fault code most common to stepper motor issues exists (P1251) and cannot be cleared after stepper motor replacement, an update to the main ECU may be required.
This can be done by Toyota dealers for around $100.
Where a fault still exists after the above calibration or upgrades have been performed, the following may need to be checked:
The correct functioning of the boost control ECU (if the car has a separate one)
The correct functioning of the main ECU
MAF sensor functioning (will generally show up as a fault code if problematic), but some say it is worth cleaning it with electrical contact cleaner anyway.
The correct functioning of the EGR valve – cleaning of which can sometimes help.
A check done of all fittings, pipes, gaskets, clamps, air cleaner & snorkel (where fitted).
A manual check done for free and easy movement of the lever that moves the vanes inside the turbo – any stickiness can be a fault inside the nozzle / vane system inside the turbo, and may show up incorrectly as a stepper motor issue.
These are just a few of the main checks that can be done to aid the diagnosis / successful install of turbo / steppers.
A cautionary note:
A faulty stepper can eventually create problems inside the turbo and vice versa.
If the vehicle is throwing codes associated with turbo or stepper motor issues including going into limp mode, it is best to tackle the issue early.
By doing so you are helping to keep the issue isolated to either part and in such case, replacement of just one part instead not replacing the entire system.
Due to the damage either part can create in the other, we do not warranty new turbochargers where the old stepper motor has been swapped across and faulted, resulting in nozzle issues in the new turbo.
It is a general recommendation that if there is a chance the stepper may be faulty as well as turbocharger, they both be replaced at the same time.
We do not supply advice on the installation of turbochargers or stepper motors beyond the information presented here on the website.
Professional installation is compulsory for warranty where a turbocharger or turbocharger / stepper motor combination or stepper motor only has been purchased.
This facilitates correct best practices for installation and diagnosis/correction of issues should they arise (as documented above).
For further information on full warranty please click here.
For a full list of the Stepper Motors and Turbo combinations we supply at the best price PLEASE CLICK HERE.
If you have any other query on matching turbo parts for your vehicle, please feel free to contact our sales support on: 0490 059 316.