Tag Archives: DTC P004B Honda

DTC P004B Turbocharger/Supercharger Boost Control ‘B’ Circuit Range/Performance

DTC P004B is a diagnostic trouble code indicating an issue with the turbocharger or supercharger boost control ‘B’ circuit, specifically related to its range or performance. Understanding and addressing this issue is crucial for maintaining your vehicle’s efficiency and performance. In this article, we’ll delve into the details of DTC P004B, exploring what it means, its potential causes, and how to diagnose and fix this issue effectively.

What is DTC P004B?

The P004B diagnostic trouble code (DTC) signifies a problem with the range or performance of the turbocharger or supercharger boost control ‘B’ circuit. The turbocharger or supercharger is a forced induction device that increases the amount of air entering the engine, thus boosting its power. The boost control circuit is responsible for regulating the amount of boost pressure the device generates. A range/performance issue means the system is not operating within its specified parameters, leading to either too much or too little boost pressure. This can result in reduced engine performance and efficiency, as well as potential damage to the engine.

Potential Causes of DTC P004B:

The P004B code is triggered when the ECM detects that the boost control ‘B’ circuit is not operating within its expected range or performance parameters. This can happen due to several reasons:

  • Faulty Boost Control Solenoid: A malfunctioning boost control solenoid can fail to regulate boost pressure correctly.
  • Wiring Issues: Damaged, corroded, or disconnected wiring in the boost control circuit can lead to range/performance issues.
  • Connector Problems: Loose or damaged connectors can disrupt the electrical pathway, affecting the circuit’s performance.
  • Boost Pressure Sensor Fault: A faulty boost pressure sensor can send incorrect data to the ECM, leading to improper boost regulation.
  • ECU Issues: A malfunctioning ECU could incorrectly interpret sensor data or fail to control the boost pressure properly.
  • Mechanical Problems: Issues with the turbocharger or supercharger itself, such as a stuck wastegate or bypass valve, can affect boost performance.

Symptoms of P004B

When the P004B code is set, you might experience the following symptoms:

  • Check Engine Light (CEL) illuminated on the dashboard.
  • Reduced engine power and performance.
  • Possible turbocharger or supercharger noise.
  • Poor fuel efficiency.
  • Delayed acceleration or inconsistent boost.

Diagnostic and Repair Procedures for DTC P004B:

Diagnosing and resolving the P004B code requires a systematic approach:

  1. Initial Inspection: Connect a diagnostic scanner to the vehicle’s OBD-II port to retrieve the trouble codes, including P004B. Record any additional codes and freeze frame data to understand the conditions under which the code was set.
  2. Visual Inspection: Conduct a thorough visual inspection of the turbocharger or supercharger boost control system and its wiring. Look for signs of damage, disconnections, or corrosion.
  3. Check Boost Control Solenoid: Test the boost control solenoid for proper operation. Ensure it regulates boost pressure correctly and receives power. Replace the solenoid if it is faulty.
  4. Inspect Wiring and Connectors: Check the wiring and connectors in the boost control circuit for continuity. Look for broken wires, loose connections, or corroded terminals. Repair or replace any damaged components.
  5. Test Boost Pressure Sensor: Verify the operation of the boost pressure sensor. Ensure it provides accurate data to the ECM. Replace the sensor if it is faulty.
  6. Inspect Turbocharger/Supercharger: Check the mechanical components of the turbocharger or supercharger, including the wastegate or bypass valve, for proper operation. Repair or replace any faulty parts.
  7. Check ECU: Although rare, inspect the ECU for any potential faults that could cause incorrect range/performance detection. Reprogram or replace the ECU if necessary.
  8. Clear Codes and Perform Test Drive: After completing the repairs, clear the trouble codes from the vehicle’s memory using the diagnostic scanner. Perform a test drive to ensure the vehicle operates properly and that the P004B code does not return.


Understanding and addressing DTC P004B is essential for maintaining optimal engine performance and preventing potential damage to the turbocharger or supercharger system. By following these detailed diagnostic and repair procedures, you can effectively address the P004B trouble code, ensuring the vehicle’s boost control system operates within its intended parameters. Regular maintenance and careful inspection of the boost control circuit can help prevent this code from appearing. If you found this guide helpful, please share it with fellow automotive enthusiasts and technicians. For more detailed guides and tips on car maintenance and repair, visit our website.