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Engine-Codes – Generic – U1421

U1421 Code - Implausible Ignition Key Off Time Received

Quick Answer

The U1421 code indicates that the Engine Control Module (ECM) has received an implausible ignition key off time signal. Common causes include Faulty ignition switch, Wiring issues or loose connections, ECM malfunction. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
U1421 indicates Implausible Ignition Key Off Time Received.
Common causes
Common causes include Faulty ignition switch, Wiring issues or loose connections, ECM malfunction.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Sep 10, 2024
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Code U1421 Description

The U1421 code indicates that the Engine Control Module (ECM) has received an implausible ignition key off time signal. In simpler terms, the ECM is not receiving the correct signal indicating when the ignition key has been turned off. This can lead to various issues within the vehicle's systems, affecting performance and potentially causing long-term damage if not addressed promptly.

OBDII Code U1421 - Implausible Ignition Key Off Time Received
U1421 Code - Implausible Ignition Key Off Time Received

Common Causes of U1421

  1. Faulty ignition switch
  2. Wiring issues or loose connections
  3. ECM malfunction
  4. Faulty ignition key
  5. Faulty ignition key reader

Symptoms of U1421

  1. Engine stalling or rough idling
  2. Difficulty starting the engine
  3. Poor fuel efficiency
  4. Check Engine Light illuminated
  5. Loss of power while driving

How to Fix U1421

  1. Begin by checking the wiring connections and ensuring they are secure and free of corrosion. Replace any damaged wires or connectors.
  2. Test the ignition switch and key reader for proper functionality. Replace any components that are faulty.
  3. Reset the ECM and clear the code. Recheck for the presence of the U1421 code.
  4. If the issue persists, consider replacing the ECM if it is determined to be faulty.
  5. Finally, perform a thorough test drive to ensure the issue has been resolved and no further codes are present.

Cost to Fix U1421

The cost of repairing the U1421 code can vary depending on the specific cause of the issue. In general, the cost of parts and labor for this repair can range from $100 to $500. Keep in mind that diagnostic time and labor rates at auto repair shops can vary, so it's best to check with local shops for a more accurate estimate. Additionally, the cost may be higher if specialized equipment or tools are required for the repair.

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Code U1421 Information for Specific Makes

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about U1421 Code

1. What does the OBDII code U1421 mean?

U1421 indicates that the vehicle's control module has received an implausible signal about the ignition key-off time, meaning the data is outside expected parameters.

2. What are the common symptoms of code U1421?

Symptoms may include the check engine light illuminating, issues with vehicle starting or shutting off, and erratic behavior in electronic systems like door locks or lighting.

3. What causes the U1421 code to appear?

Common causes include a faulty ignition switch, a failing body control module (BCM), wiring issues, or corrupted communication signals between modules.

4. Can a weak battery cause the U1421 code?

Yes, a weak or failing battery can cause voltage irregularities that may trigger the U1421 code.

5. How do you diagnose the U1421 code?

Diagnosis involves scanning for additional codes, checking the wiring and connectors for damage, testing the ignition switch, and verifying module communication using specialized diagnostic tools.

6. Is the U1421 code serious?

While it may not immediately affect drivability, ignoring the code can lead to further electrical issues or starting problems over time.

7. Can I clear the U1421 code without fixing the issue?

Clearing the code without addressing the underlying problem may cause it to reappear and potentially worsen the vehicle's symptoms.

8. How do you fix the U1421 code?

Repairs may include replacing a faulty ignition switch, repairing damaged wiring, reprogramming or replacing the BCM, or addressing battery and voltage issues.

9. Can a software update resolve the U1421 code?

In some cases, a dealer-performed software update for the vehicle’s control modules can resolve communication errors causing the code.

10. What tools are needed to troubleshoot the U1421 code?

A professional-grade OBDII scanner, a multimeter for testing wiring, and access to the vehicle’s wiring diagrams are essential for diagnosing this code.

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