AutoCodes – Generic – P305D

P305D 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 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 6,186

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

What does this mean?

What are the Possible Causes of the DTC P305D?

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?

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 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 code?

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

Need Help with the Code?

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

Information for Specific Makes

P305D Buick — DC/DC Converter Crank Control Circuit High Voltage
P305D Cadillac — DC/DC Converter Crank Control Circuit High Voltage
P305D Chevrolet — DC/DC Converter Crank Control Circuit High Voltage
P305D GMC — DC/DC Converter Crank Control Circuit High Voltage

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 Code

1. What does the OBDII code P305D mean?

P305D indicates a high voltage issue in the DC/DC converter crank control circuit, which is responsible for managing electrical power distribution in vehicles with advanced electrical systems.

2. What are the symptoms of the P305D code?

Common symptoms include difficulty starting the engine, dim or flickering lights, warning lights on the dashboard, or loss of power to certain electrical components.

3. What causes the P305D code to appear?

Potential causes include a malfunctioning DC/DC converter, damaged or corroded wiring, a faulty control module, or a failing battery or alternator.

4. Can I drive my car with the P305D code active?

While you may be able to drive the car, it is not recommended. The code can indicate electrical system issues that may worsen over time, potentially leading to a breakdown.

5. How do I diagnose the P305D code?

Diagnose the code by inspecting the DC/DC converter, checking for damaged or corroded wiring, testing the battery and alternator, and using a scan tool to monitor voltage levels.

6. How is the P305D code fixed?

Repairs may involve replacing or repairing the DC/DC converter, fixing damaged wiring or connectors, reprogramming or replacing the control module, or addressing battery and alternator issues.

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

Youâ€™ll need a multimeter to check voltage and continuity, a diagnostic scan tool to read and clear codes, and possibly wiring diagrams for the vehicle.

8. Can a low battery cause the P305D code?

Yes, a low or failing battery can cause voltage irregularities, potentially triggering the P305D code.

9. How much does it cost to fix the P305D code?

Repair costs can vary widely depending on the root cause, ranging from $100 for minor wiring repairs to over $1,000 if the DC/DC converter needs replacement.

10. How can I prevent the P305D code from occurring?

Regularly inspect and maintain the electrical system, ensure the battery and alternator are in good condition, and address any warning signs of electrical issues promptly.