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P1778 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P1778 is an OBD-II Code that refers to Step Motor Function


A P1778 code is a Nissan diagnostic trouble code that occurs when the PCM/ECM receives a signal indicating a problem with the step motor function. The four stages of the step motor have several variations depending on the signal sent by the TCM (Transmission Control Module). As a result, the flow of line pressure to the primary pulley is altered, and the pulley ratio is maintained. This conclusion is reached when the electrical system is in good order, but there are problems with the mechanical system. The device is also capable of recognizing when the state of the speed change mechanism in the unit deviates from normal.

When the TCM detects an anomaly in the step motor function or circuit, it will set a P1778 code.


Common causes for this code include:

  • Bad Step Motor 
  • Step Motor harness is open or shorted 
  • Step Motor circuit poor wiring and connection


The symptoms of a P1778 code are:

  • MIL is illuminated
  • Normally no other noticeable symptoms


To diagnose a P1778 DTC code, a technician would:

  1. Scan for codes in the ECM and look at the freeze frame data for failure.
  2. Visually inspect the wiring and connectors for damage.
  3. Check the voltage at the step motor.
  4. Measure the resistance of the step motor.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P1778 code:

  • Not thoroughly inspecting all the wiring and connectors.
  • Not checking the voltage at the step motor.
  • Not checking the resistance of the step motor.

How serious is this?

A P1778 code is not a particularly serious code, but it can indicate a problem with the charging system. If the code is not corrected, it may eventually lead to a more serious issue.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Bad wiring, connectors, and modules repaired or replaced
  • Replacing the step motor

Related codes

A P1778 is related to and may be accompanied by the following codes:

P0128 – Coolant Temperature Below Thermostat Regulating Temperature

P1299 – Step Motor Function (ELD)


In conclusion, the P1778 code is a diagnostic trouble code that refers to a problem with the step motor function. The code may be caused by a bad step motor, a shorted or open step motor harness, or poor wiring and connections. The code is not particularly serious, but it can indicate a problem with the charging system that should be corrected.