Warning: Disconnect power before servicing.
ErrBase

Generac Generator Code 1603: Stepper Overcurrent

Quick Answer

Generac 1603 is a fault code on Generac standby generators. Code 1603 indicates the controller detected excessive current draw from the governor stepper motor (iSMA). The motor is either shorted or mechanically jammed.

Generac 1603 is a fault code on Generac standby generators. Code 1603 indicates the controller detected excessive current draw from the governor stepper motor (iSMA). The motor is either shorted or mechanically jammed. The Generac Evolution controller stores fault history accessible by pressing OFF then ENTER twice. This code should be addressed promptly to ensure the generator is ready for the next power outage.

GeneracGeneratorSeverity: highDifficulty: intermediate75% DIY Success
Time to Fix
30–180 min
Difficulty
intermediate
Parts Cost
—
Tools Needed
Multimeter, Socket wrench set

What Does the 1603 Code Mean?

Code 1603 indicates the controller detected excessive current draw from the governor stepper motor (iSMA). The motor is either shorted or mechanically jammed.

Most Likely Causes

Based on aggregated repair data, here is the probability breakdown for this error code:

iSMA stepper motor winding shorted40%
Governor linkage mechanically jammed24%
Controller driver over-driving actuator14%
Actuator seized from corrosion12%
Wiring short in actuator harness10%

Symptoms You May Notice

  • Code 1603 on controller display
  • Generator alarm light active
  • Generator may have shut down
  • Audible alarm from controller

Can you reset a Generac generator to clear the 1603 code?

Press ALARM RESET on the controller. Switch to AUTO for standby mode. Test with MANUAL RUN to verify fix.

Tools Required for Diagnosis

MultimeterSocket wrench setFlashlight

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

1

Read and note the 1603 alarm code from the controller display

Read and note the 1603 alarm code from the controller display. Press OFF then ENTER twice to check fault history.

2

Press ALARM RESET to clear the code

3

Based on the specific code, inspect the related component

Frequently Asked Questions

Is Generac code 1603 serious?
Code 1603 indicates isma stepper motor winding shorted. While not always an emergency, it means your generator may not be ready for the next power outage. Address it at your next service visit or sooner if outages are expected.
Can I reset code 1603 myself?
Yes. Press the ALARM RESET button on the controller. If the code returns immediately, the fault is still active. If it clears and stays clear through the next exercise cycle, it was likely a transient condition.
Should I call a Generac dealer for this code?
If the code returns after reset, or if you are not comfortable diagnosing engine and electrical systems, yes. Generac authorized dealers have diagnostic software that provides more detail than the controller display alone.

Related Generac Generator Error Codes

Code: HUBGenerac Generator Error Codes: Complete Reference

Models Known to Experience 1603 Errors

This repair applies to most Generac generators with this error code. Common model numbers include:

Guardian 22kW 7043, Guardian 24kW 7210, Guardian 16kW 7035, EcoGen 15kW, Protector 20kW

Last verified for technical accuracy on March 15, 2026