AutoCodes – Subaru – B0401 Subaru

B0401 Subaru Code - M Collation NG

Quick Answer

The Immobilizer system performs the starter relay control. Common causes include Incorrect Immobilizer Key, Immobilizer Key Not Programmed, Faulty Body Integrated Unit (BIU). 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: B0401 Subaru indicates M Collation NG.
Common causes: Common causes include Incorrect Immobilizer Key, Immobilizer Key Not Programmed, Faulty Body Integrated Unit (BIU).
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 6,217

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 Mar 11, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B0401 Subaru Description

The Immobilizer system performs the starter relay control. The Body Integrated Unit (BIU) detects the inconformity of reference code, immediately output the starter relay cut signal to Engine Control Module (ECM), and then ECM stops the starter relay operation. In this case, engine does not start, and DTC is not recorded in ECM. Check that the engine does not start on the DTC of body integrated unit.

OBDII Code B0401 Subaru - M Collation NG - AutoCodes.com — B0401 Subaru Code - M Collation NG

What does this mean?

What are the Possible Causes of the DTC B0401 Subaru?

Incorrect Immobilizer Key
Immobilizer Key Not Programmed
Faulty Body Integrated Unit (BIU)

How to Fix the DTC B0401 Subaru?

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 B0401 Subaru 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.

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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 B0401 Subaru Code

1. What are the common symptoms of OBDII code B0401 in a Subaru?

The common symptoms include difficulty starting the vehicle, rough idling, and a noticeable decrease in fuel efficiency.

2. What could cause OBDII code B0401 to appear in a Subaru?

The code is typically triggered by a malfunction in the M Collation NG system, which is responsible for monitoring and controlling various engine functions.

3. How serious is OBDII code B0401 in a Subaru?

While the code itself may not cause immediate harm to the vehicle, ignoring it can lead to further damage and potentially more expensive repairs down the line.

4. Can I still drive my Subaru with OBDII code B0401?

It is generally not recommended to drive the vehicle with an active OBDII fault code, as it indicates a problem that should be addressed promptly to prevent any potential issues.

5. How can I diagnose OBDII code B0401 in my Subaru?

Diagnosing the code usually involves using an OBDII scanner to retrieve the specific fault code, followed by a thorough inspection of the M Collation NG system components.

6. Are there any DIY repair tips for fixing OBDII code B0401 in a Subaru?

DIY repair for this code may include checking for loose electrical connections, replacing faulty sensors, or cleaning components within the M Collation NG system.

7. Is it necessary to visit a mechanic for OBDII code B0401 in a Subaru?

While some basic troubleshooting can be done at home, seeking professional help from a qualified mechanic is advisable to accurately diagnose and repair the issue.

8. How much does it typically cost to fix OBDII code B0401 in a Subaru?

The cost of repairing this code can vary depending on the root cause of the issue, but it is recommended to budget for diagnostic fees, parts replacement, and labor costs.

9. Can resetting the OBDII system clear OBDII code B0401 in a Subaru?

Resetting the OBDII system may temporarily clear the code, but if the underlying issue is not addressed, it is likely to reappear once the problem resurfaces.

10. How can I prevent OBDII code B0401 from recurring in my Subaru?

Regular maintenance, timely repairs, and addressing any issues promptly can help prevent the reoccurrence of OBDII code B0401 in your Subaru.