AutoCodes – Subaru – B0403 Subaru

B0403 Subaru Code - E/G Request 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: B0403 Subaru indicates E/G Request 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 6,236

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 B0403 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 B0403 Subaru - E/G Request NG - AutoCodes.com — B0403 Subaru Code - E/G Request NG

What does this mean?

What are the Possible Causes of the DTC B0403 Subaru?

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

How to Fix the DTC B0403 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 B0403 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 B0403 Subaru Code

1. What does OBDII code B0403 Subaru (E/G Request NG) indicate?

The code B0403 Subaru (E/G Request NG) signifies a communication issue between the engine control module (ECM) and the transmission control module (TCM).

2. What are the common symptoms of OBDII code B0403 Subaru?

Common symptoms of code B0403 may include transmission shifting problems, engine stalling, rough idling, and an illuminated check engine light.

3. What are the possible causes of OBDII code B0403 Subaru?

Potential causes of code B0403 include faulty wiring or connectors between the ECM and TCM, a malfunctioning ECM or TCM, or a communication error between the two modules.

4. How can I diagnose OBDII code B0403 Subaru?

Diagnosing code B0403 typically involves using an OBDII scanner to retrieve the code, checking the wiring and connectors between the ECM and TCM for any damage, and performing a thorough inspection of the ECM and TCM.

5. How can I repair OBDII code B0403 Subaru?

To repair code B0403, you may need to repair or replace any damaged wiring or connectors, reset the ECM and TCM, or replace the faulty ECM or TCM if necessary.

6. Can I drive my Subaru with OBDII code B0403?

It is not recommended to drive your Subaru with an active B0403 code as it can lead to potential transmission and engine issues. It's best to address the problem promptly.

7. How much does it cost to fix OBDII code B0403 Subaru?

The cost of fixing code B0403 can vary depending on the underlying cause. Simple fixes such as repairing wiring may be relatively inexpensive, while replacing the ECM or TCM can be more costly.

8. Is OBDII code B0403 Subaru a serious issue?

While code B0403 may not always result in immediate drivability issues, it can lead to more serious problems if left unaddressed, such as transmission or engine damage.

9. Can a DIY enthusiast fix OBDII code B0403 Subaru?

DIY enthusiasts with automotive repair knowledge and access to the proper tools may be able to diagnose and repair code B0403. However, complex issues may require professional assistance.

10. How often does OBDII code B0403 Subaru occur in Subaru vehicles?

While not as common as some other OBDII codes, B0403 can still occur in Subaru vehicles, especially in older models or those with high mileage. Regular maintenance can help prevent such issues.