AutoCodes – Generic – U1421

U1421 Code - Implausible Ignition Key Off Time Received

Quick Answer

The Body Control Module (BCM) monitors the time the ignition is in the off or accessory position between key cycles and then broadcasts the signal called Ignition Off Time (IOT) via the CANC Bus. Common causes include Faulty Body Control Module (BCM), Body Control Module (BCM) harness is open or shorted, Body Control Module (BCM) circuit poor electrical connection. 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 Body Control Module (BCM), Body Control Module (BCM) harness is open or shorted, Body Control Module (BCM) circuit poor electrical connection.
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.

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Code Popularity 9,226

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on May 23, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U1421 Description

The Body Control Module (BCM) monitors the time the ignition is in the off or accessory position between key cycles and then broadcasts the signal called Ignition Off Time (IOT) via the CANC Bus. The Powertrain Control Module (PCM) saves the value from a previous key cycle into powerdown flash and if certain When Monitored conditions are met compares to the current value. If the Set Conditions are met, then a fault U1421 is set indicating the timer is stuck. If this fault becomes active the PCM will light the MIL light immediately. If the MIL is set and the fault goes stored the PCM turns off the MIL after 3 consecutive drive cycles. If the difference between two Ignition Off Times (IOT) sent from the BCM to the PCM during two separate diagnostic decisions is less than 3 minutes for 5 consecutive decisions this fault will set.

OBDII Code U1421 - Implausible Ignition Key Off Time Received - AutoCodes.com — U1421 Code - Implausible Ignition Key Off Time Received

What does this mean?

What are the Possible Causes of the DTC U1421?

Faulty Body Control Module (BCM)
Body Control Module (BCM) harness is open or shorted
Body Control Module (BCM) circuit poor electrical connection
Faulty Powertrain Control Module (PCM)

How to Fix the DTC U1421?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U1421 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the U1421 code?

Need more information on how to fix the U1421 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U1421 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U1421 Chrysler — Implausible Ignition Key Off Time Received
U1421 Dodge — Implausible Ignition Key Off Time Received
U1421 Jeep — Implausible Ignition Key Off Time Received
U1421 RAM — Implausible Ignition Key Off Time Received

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 vehicleâ€™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 vehicleâ€™s wiring diagrams are essential for diagnosing this code.