AutoCodes – Subaru – B0402 Subaru

B0402 Subaru Code - Immobilizer Key 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: B0402 Subaru indicates Immobilizer Key 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 11,977

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 B0402 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 B0402 Subaru - Immobilizer Key Collation NG - AutoCodes.com — B0402 Subaru Code - Immobilizer Key Collation NG

What does this mean?

What are the Possible Causes of the DTC B0402 Subaru?

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

How to Fix the DTC B0402 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 B0402 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 B0402 Subaru Code

1. What are the common symptoms of OBDII code B0402 Subaru Immobilizer Key Collation NG?

- Common symptoms include the inability to start the vehicle, the engine not turning over, and the security light staying illuminated.

2. What causes the OBDII code B0402 Subaru Immobilizer Key Collation NG?

- This code is typically triggered by a mismatch between the immobilizer key and the vehicle's security system, often due to a faulty key, key programming issue, or immobilizer module malfunction.

3. How can I diagnose the OBDII code B0402 Subaru Immobilizer Key Collation NG?

- Diagnosis involves checking the immobilizer key, verifying key programming, and inspecting the immobilizer module for any faults using a diagnostic scan tool.

4. Can I fix the OBDII code B0402 Subaru Immobilizer Key Collation NG myself?

- While some simple key reprogramming procedures can be done at home, resolving more complex issues with the immobilizer system may require professional assistance from a dealership or qualified mechanic.

5. Are there any temporary solutions if I encounter the OBDII code B0402 Subaru Immobilizer Key Collation NG?

- In some cases, disconnecting the battery for a few minutes and then reconnecting it may reset the immobilizer system and allow the vehicle to start temporarily. However, this is not a permanent solution.

6. How much does it typically cost to repair the OBDII code B0402 Subaru Immobilizer Key Collation NG?

- The cost of repairs can vary depending on the exact cause of the issue, but it may range from a simple key reprogramming cost to a more expensive immobilizer module replacement.

7. Can a faulty key fob trigger the OBDII code B0402 Subaru Immobilizer Key Collation NG?

- Yes, a faulty key fob or a key that is not properly programmed can trigger this code, leading to immobilizer key collation issues.

8. Is it safe to continue driving with the OBDII code B0402 Subaru Immobilizer Key Collation NG active?

- It is not recommended to drive the vehicle with this code active, as it may result in the vehicle not starting at all, leading to potential inconvenience or safety concerns.

9. Will resetting the ECU clear the OBDII code B0402 Subaru Immobilizer Key Collation NG?

- Resetting the ECU may temporarily clear the code, but it is likely to return if the underlying issue with the immobilizer key collation is not addressed.

10. How can I prevent encountering the OBDII code B0402 Subaru Immobilizer Key Collation NG in the future?

- To prevent this code from appearing in the future, ensure that your immobilizer key is in good condition, properly programmed, and that the immobilizer system is regularly maintained according to the manufacturer's recommendations.