Electronic Actuator Stepper Motor Information
Stepper Motor and Turbochargers
The Electronic Actuator Stepper Motor on turbochargers move the vanes inside a VNT (Variable Nozzle Technology) turbo.
The variable vanes do 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.
And it is the Nozzle or Excitor ring is actuated by the stepper motor.
Why ‘Calibration’ of the Stepper Motor is Sometimes Required
We supply both Stepper Motors and Turbochargers to the market.
We sell the separate components to allow the purchase of either part, depending on the problem they are purchased to fix.
But we also offer complete, flow-tested units, where the actuator is attached to the turbo and tested at the factory. And where the turbocharger and stepper motor are sold together, there is a substantial discount to purchasing separately.
Installing the old or new stepper (where a component is purchased separately), involves only 3 bolts.
Additionally, the actuator arm is attached via a clip to the stepper. And the other end of the arm also attaches via a clip to the lever that actuates (moves) the vanes inside the turbo.
Once the electronic actuator stepper motor is attached to the turbo, it should work immediately with very little adjustment.
But, 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. This code persists even after the new stepper / turbo has been installed.
An example code would be: P0047 which relates to stepper motor. This may indicate low voltage or an out of range boost pressure detected.
Or cases where insufficient boost has been attained or general over-boost fault codes are thrown by the ECU.
And includes cases where the vehicle goes into ‘limp’ mode to protect engine components.
Stepper Motors and Fault Codes
Because of the general nature of fault codes, they can seem to emulate the same issue as the original fault that called for replacement.
But codes usually lump 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. It may be that the stepper just requires some calibration.
Another example is where the problem exists outside of the turbo/stepper system. The fault may exist in the ECU unit that controls the stepper. Or 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.
This will 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.
Stopper adjustments are made in small increments and testing of flow and boost done between adjustments.
Stoppers should be adjusted with small increments of 1/16 of a full turn and then tested.
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 as follows:
Slightly loosen 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.
What if Stepper Motor Calibration doesn’t Work?
Where a fault still exists after the above calibrations 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 may be worth cleaning with electrical contact cleaner.
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 is usually a fault inside the nozzle / vane system inside the turbo. And is usually due to excessive coking inside the vane assembly due to incorrect engine combustion (obviously not in a new turbo install).
Either of these 2 issues above, 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. Whereby the faulty old stepper has created 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.