P1521 – OBD-II DTC

OBD-II DTC P1521 – IMRC Input Error (Bank 1)

DTC P1521 meaning

DTC P1521 refers to an “IMRC Input Error (Bank 1)” in the On-Board Diagnostics II (OBD-II) system. The IMRC, or Intake Manifold Runner Control, is responsible for optimizing the airflow into the engine by adjusting the position of the intake manifold runners. This code indicates that the Engine Control Module (ECM) has detected a malfunction in the IMRC system for bank 1, which can lead to performance issues and increased emissions.

DTC P1521 symptoms

Common symptoms associated with DTC P1521 may include:

• Check Engine Light illuminated
• Reduced engine performance
• Rough idling or stalling
• Decreased fuel efficiency
• Unusual engine noises

DTC P1521 causes

Several factors can trigger DTC P1521, including:

• Faulty IMRC actuator
• Damaged or disconnected vacuum lines
• Electrical issues such as short circuits or open circuits in the IMRC circuit
• Faulty throttle position sensor
• Contaminated or damaged intake manifold

DTC P1521 seriousness

DTC P1521 can be considered a moderate to serious issue. While it may not cause immediate catastrophic failure, it can lead to:

• Decreased engine performance
• Increased emissions, potentially failing emissions tests
• Long-term engine damage if left unaddressed

How to diagnose DTC P1521

To diagnose DTC P1521, follow these steps:

1. Use an OBD-II scanner to confirm the presence of the P1521 code.
2. Inspect the IMRC actuator and its connections for any visible damage or disconnections.
3. Check for vacuum leaks in the lines connected to the IMRC system.
4. Test the IMRC actuator for proper operation using a multimeter.
5. Examine the throttle position sensor and its wiring for faults.
6. Clear the code and perform a test drive to see if the code reappears.

How to fix DTC P1521 step-by-step instructions

To fix DTC P1521, follow these steps:

1. Inspect and repair any damaged wiring or connectors related to the IMRC actuator.
2. Replace any faulty vacuum lines that may be causing leaks.
3. Test and replace the IMRC actuator if it is not functioning correctly.
4. Check and replace the throttle position sensor if it is found to be faulty.
5. Clean the intake manifold if it is contaminated or clogged.
6. Clear the DTC using an OBD-II scanner and perform a test drive to ensure the issue is resolved.

How to erase DTC P1521

To erase DTC P1521, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn on the ignition without starting the engine.
3. Navigate to the “Erase Codes” or “Clear Codes” option on the scanner.
4. Confirm the action to clear the DTC from the ECM.
5. Disconnect the scanner and start the engine to verify that the code does not reappear.

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