Stepper Motor Fault Codes

Stepper Motor Fault Codes

What are Electronic Actuator / Stepper Motor Fault Codes?


Stepper Motor Fault Codes are ‘thrown’ or produced by the ECU. Codes show up as engine management light(MIL) illuminated on dash to alert that a code is in memory, waiting to be read.
An electronic tool (scanner) is used to read the codes stored. Once read and the diagnostics competed with issue resolved, the code can then be cleared from ECU memory.

Generally, these codes do not give exact, specific information into the nature of the issue. Rather they are used as a beginning guide for diagnosis.

A General note on Fault Codes:

Fault codes are non-specific and after installing a new turbo or stepper motor, you may see the same code again.
Faulty deduction would lead to assuming that the replacement part is faulty as well.
For example, faulty stepper motor throws a P1250 code and is replaced. The new stepper trips the same fault code, so suspected as faulty.
In such case it is more likely the new stepper motor requires some calibration.

Warning: Do not ignore Fault Codes

If the vehicle’s turbo or stepper motor is throwing codes and especially if the car has gone into ‘limp mode’, do not ignore the warning.
Leaving things to get worse can mean the faulty stepper eventually damages the turbocharger or a jammed VNT system quickly damages the cogs inside the stepper motor.

Acting quickly, may mean you can isolate the issue to either part. Needing only to replace the faulty part and not the entire turbo/stepper as a unit.

Typical Fault Codes

Error code P1251: stepper motor intermittent
This is the most common code you will see especially with Toyota vehicles.
A modified vehicle, may throw this code, along with engine management ‘limp’ mode activation.
This can be a false-positive. Whereby the issue is not the actual stepper, but a related component, system or modification at fault.
– The most common ‘mod’ is a high flow (usually 3″) exhaust, it is the most common reason for a false positive.
– Injector modification that increases fuel flow can also be a reason for a false positive code.
– Actual failure of the stepper motor. Not a false positive, and requires that the stepper motor be replaced.
– Failure of the turbocharger. A false positive of sorts, as not directly due to stepper motor failure. Occurs when the nozzle ring (VNT assembly) in the turbine housing become seized. Requires that the turbo be replaced, and if left too long, likely the stepper motor as well.

This often happens due to excess coking inside the assembly. Read more about this and how to check if this issue exists here!.

Error code P0047: low voltage or boost pressure out of range
Error code P2034 & P1250: usually high boost pressure out of range but may also indicate the opposite

With reference to Stepper Motors and new installs of a stepper unit, the above 2 codes may indicate that the stepper requires ‘calibration’ to the turbocharger.

What if codes persist and I need a new stepper or turbocharger?

Should the stepper motor fault codes persist, despite checks and diagnosis we have a range of turbos (with upgrades) and stepper’s available.
Here is a list of cost-effective aftermarket turbocharger electric stepper motor actuators we have in stock at the best prices, covered by our Exclusive 24 Month Warranty.

Alternatively, here is our range of complete factory-calibrated (flow tested) units with stepper motors attached.
We have ceramic and high-flow billet upgrades that we hold in stock, and reconditioned units at the best prices, also covered by our Exclusive 24 Month Warranty.

If you need any further information, or help in matching parts to your vehicle, please contact our sales line: 0490 059 316.