AutoCodes – Buick – P305D Buick

P305D Buick Code - DC/DC Converter Crank Control Circuit High Voltage

Quick Answer

The Power Supply Transformer is used to boost battery voltage to sensitive loads during engine restart. Common causes include Faulty Power Supply Transformer, Power Supply Transformer harness is open or shorted, Power Supply Transformer circuit poor 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: P305D Buick indicates DC/DC Converter Crank Control Circuit High Voltage.
Common causes: Common causes include Faulty Power Supply Transformer, Power Supply Transformer harness is open or shorted, Power Supply Transformer circuit poor 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 2,882

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 May 16, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code P305D Buick Description

The Power Supply Transformer is used to boost battery voltage to sensitive loads during engine restart. It provides two voltage outputs that provide the boosted voltage. The Power Supply Transformer communicates to the Engine Control Module (ECM), and sends to the ECM the state of the crank control input.

OBDII Code P305D Buick - DC/DC Converter Crank Control Circuit High Voltage - AutoCodes.com — P305D Buick Code - DC/DC Converter Crank Control Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P305D Buick?

Faulty Power Supply Transformer
Power Supply Transformer harness is open or shorted
Power Supply Transformer circuit poor electrical connection

How to Fix the DTC P305D Buick?

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 P305D Buick 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 P305D Buick code?

Need more information on how to fix the P305D Buick code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P305D Buick code diagnosed by a professional: Find a repair shop in your area

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 P305D Buick Code

1. What does the OBDII code P305D mean on a Buick?

The P305D code indicates a high voltage issue in the DC/DC converter crank control circuit, which manages voltage between the 12V and high-voltage systems.

2. What are the common symptoms of the P305D code in a Buick?

Symptoms may include a check engine light, difficulty starting the vehicle, dim or flickering headlights, or electrical system malfunctions.

3. What causes the P305D code to appear?

Possible causes include a faulty DC/DC converter, damaged wiring or connectors in the crank control circuit, or issues with the vehicleâ€™s battery or alternator.

4. Can I drive my Buick with the P305D code?

Driving with this code is not recommended as it may lead to electrical system failures or leave you stranded if the battery becomes unable to power the vehicle.

5. How do I diagnose the P305D code on my Buick?

Diagnosis involves using a multimeter to check for high voltage in the crank control circuit, inspecting wiring and connectors, and testing the functionality of the DC/DC converter.

6. How do I fix the P305D code on a Buick?

Repairs may include replacing the DC/DC converter, repairing damaged wiring or connectors, or ensuring the battery and alternator are functioning correctly.

7. What tools are needed to address the P305D code?

Youâ€™ll typically need an OBDII scanner, a multimeter, and basic automotive tools to diagnose and repair the issue.

8. Is the P305D code specific to hybrid or electric Buicks?

Yes, this code is more common in hybrid or electric vehicles due to their use of high-voltage systems and DC/DC converters.

9. How much does it cost to repair the P305D code on a Buick?

Repair costs can vary widely, ranging from $100 to $1,000 or more, depending on whether the issue is a simple wiring repair or a full DC/DC converter replacement.

10. Can a dead 12V battery cause the P305D code?

Yes, a weak or dead 12V battery can cause voltage irregularities and trigger the P305D code.