DTC P0387 Crankshaft Position Sensor B Circuit Low Input

In the intricate world of automotive diagnostics, On-Board Diagnostic Trouble Codes (DTCs) play a vital role in identifying and rectifying issues within your vehicle. In this insightful blog post, we will unravel the mysteries of DTC P0387, focusing on the Crankshaft Position Sensor B Circuit Low Input problem. Whether you’re a passionate automotive enthusiast or a seasoned mechanic, this comprehensive guide will equip you with the knowledge and steps to diagnose and address this particular trouble code. Let’s embark on this diagnostic journey.

1. Understanding P0387: Deciphering the Code

DTC P0387 is a diagnostic trouble code that signifies a low input signal in the Crankshaft Position Sensor B Circuit. The Crankshaft Position Sensor, a critical component of the engine management system, monitors the position and rotational speed of the crankshaft. When it detects a lower-than-expected input signal, the Engine Control Module (ECM) triggers the P0387 code, indicating a potential issue with the sensor or its circuit.

2. Exploring the Origins: What Causes P0387?

To effectively diagnose and resolve DTC P0387, it’s essential to grasp the various potential causes, which may include:

  • A malfunctioning or damaged crankshaft position sensor.
  • Wiring issues, such as shorts, breaks, or corroded connections in the sensor’s circuit.
  • Poor electrical connections or connector corrosion.
  • Infrequent problems with the ECM. Identifying the root cause is the initial step toward rectifying this code.

3. Recognizing the Symptoms: What to Look For

Recognizing the symptoms associated with DTC P0387 is crucial for early detection. Common signs of this issue include:

  • Engine misfires or hesitation during acceleration.
  • Difficulty starting the engine, especially in cold conditions.
  • An illuminated check engine light (CEL) on the dashboard.
  • Reduced engine performance and power. If you encounter any of these symptoms, addressing the issue promptly is essential to prevent further engine complications.

4. Diagnosing DTC P0387: A Step-by-Step Approach

Accurate diagnosis of DTC P0387 requires a systematic approach. Here’s a step-by-step guide to help you pinpoint the issue:

5. Resolving P0387: How to Address the Problem

Once you’ve identified the issue causing DTC P0387, it’s time to address it effectively. Consider these steps:

  • Replace the crankshaft position sensor if it is determined to be faulty or damaged.
  • Repair or replace any damaged wiring or connectors in the Crankshaft Position Sensor B Circuit.
  • Ensure proper electrical connections and clean any corroded connectors.
  • Clear the trouble code using your OBD-II scanner after completing the necessary repairs. Clearing the code is crucial to reset the check engine light and confirm that the problem has been successfully resolved.


In this comprehensive guide, we’ve navigated through DTC P0387, the Crankshaft Position Sensor B Circuit Low Input code. Understanding its meaning, potential causes, symptoms, systematic diagnosis, and the importance of clearing the trouble code empowers you to confidently address this issue. Whether you’re a dedicated automotive enthusiast or a skilled mechanic, resolving these challenges with precision not only restores your vehicle’s performance but also elevates your automotive knowledge. Wishing you smooth and trouble-free journeys!