AutoCodes – Generic – B278A

B278A Code - Short to GND in Immobiliser System Power Source Circuit

Quick Answer

When there is a short to GND in the power supply for the Transponder Key Amplifier of the Engine Switch, the Certification ECU (Smart Key ECU Assembly) stores this Diagnostic Trouble Code (DTC). Common causes include Faulty Engine Switch, Engine Switch harness is open or shorted, Engine Switch circuit 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: B278A indicates Short to GND in Immobiliser System Power Source Circuit.
Common causes: Common causes include Faulty Engine Switch, Engine Switch harness is open or shorted, Engine Switch circuit 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 1,632

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 Jan 16, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B278A Description

When there is a short to GND in the power supply for the Transponder Key Amplifier of the Engine Switch, the Certification ECU (Smart Key ECU Assembly) stores this Diagnostic Trouble Code (DTC).

OBDII Code B278A - Short to GND in Immobiliser System Power Source Circuit - AutoCodes.com — B278A Code - Short to GND in Immobiliser System Power Source Circuit

What does this mean?

What are the Possible Causes of the DTC B278A?

Faulty Engine Switch
Engine Switch harness is open or shorted
Engine Switch circuit electrical connection
Faulty Certification ECU (Smart Key ECU Assembly)

How to Fix the DTC B278A?

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 B278A 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 B278A code?

Need more information on how to fix the B278A code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B278A code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

B278A Lexus — Short to GND in Immobiliser System Power Source Circuit
B278A Nissan — Electric Compressor Low Voltage
B278A Scion — Short to GND in Immobiliser System Power Source Circuit
B278A Toyota — Short to GND in Immobiliser System Power Source Circuit

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 B278A Code

1. What are the common symptoms of OBDII code B278A (Short to GND in Immobiliser System Power Source Circuit)?

- Common symptoms include difficulty starting the vehicle, intermittent stalling, and the immobilizer system malfunctioning.

2. What are the possible causes of OBDII code B278A?

- Possible causes include damaged wiring in the immobilizer system circuit, a faulty immobilizer control module, or a short to ground in the power source circuit.

3. How can I diagnose OBDII code B278A?

- Diagnosing this code involves performing a thorough inspection of the wiring in the immobilizer system circuit, testing the immobilizer control module, and checking for any shorts to ground in the power source circuit.

4. Can I still drive my vehicle with OBDII code B278A present?

- It is not recommended to drive the vehicle with this code present, as it may lead to issues with starting the engine or the immobilizer system functioning properly.

5. How can I repair OBDII code B278A?

- Repairing this code typically involves repairing or replacing damaged wiring in the immobilizer system circuit, replacing the immobilizer control module if necessary, and addressing any shorts to ground in the power source circuit.

6. Is it safe to reset the OBDII code B278A with a diagnostic tool?

- It is safe to reset the code temporarily to see if it reoccurs after making repairs. However, it is crucial to address the underlying issue causing the code to prevent further problems.

7. Can a DIYer fix OBDII code B278A at home?

- While some basic troubleshooting steps can be performed at home, diagnosing and repairing OBDII code B278A may require advanced knowledge and tools. It is recommended to seek professional help for proper diagnosis and repair.

8. How much does it cost to repair OBDII code B278A?

- The cost of repairing this code can vary depending on the extent of the issue and the specific repairs needed. It is advisable to obtain quotes from automotive professionals for an accurate estimate.

9. Will OBDII code B278A cause a vehicle to fail an emissions test?

- Yes, OBDII code B278A can cause a vehicle to fail an emissions test due to the potential impact on the immobilizer system, which is an essential component for proper vehicle operation.

10. How long does it take to repair OBDII code B278A?

- The repair time for OBDII code B278A can vary based on the complexity of the issue and the availability of parts. It is best to consult with a mechanic to get an estimated timeframe for the repair.