AutoCodes – Generic – B0402

B0402 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 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 1,927

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

What does this mean?

What are the Possible Causes of the DTC B0402?

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

How to Fix the DTC B0402?

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 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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Information for Specific Makes

B0402 Subaru — Immobilizer Key Collation NG

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.