P305C Buick Code - DC/DC Converter Ignition On/Start Switch Circuit Low Voltage
Quick Answer
The Body Control Module (BCM) controls the ignition main relay through the control circuit by applying voltage to the circuit. 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
- P305C Buick indicates DC/DC Converter Ignition On/Start Switch Circuit Low 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.
Code P305C Buick Description
What are the Possible Causes of the DTC P305C 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 P305C 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 P305C 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 P305C Buick code?
Need more information on how to fix the P305C Buick code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P305C Buick code diagnosed by a professional: Find a repair shop in your area
Frequently Asked Questions about P305C Buick Code
What does the OBDII code P305C mean for a Buick?
The code P305C indicates a low voltage problem in the DC/DC converter ignition on/start switch circuit, which converts power for hybrid or electrical components.
What are the common symptoms of code P305C in a Buick?
Symptoms may include a check engine light, failure to start, reduced hybrid system performance, or electrical issues in the vehicle.
What causes the P305C code to appear in a Buick?
Common causes include a faulty DC/DC converter, damaged wiring, corroded connectors, or a weak or failing 12V auxiliary battery.
Can a dead battery trigger the P305C code in a Buick?
Yes, a weak or failing 12V auxiliary battery can result in insufficient voltage, triggering the P305C code.
How is the P305C code diagnosed in a Buick?
A mechanic will use a scan tool to confirm the code, inspect the DC/DC converter, check wiring and connectors, and test the auxiliary battery for proper voltage output.
Can you drive a Buick with the P305C code active?
Driving with this code is not recommended, as it may lead to electrical system failures or prevent the vehicle from starting.
How much does it cost to fix the P305C code on a Buick?
Repair costs vary but may range from $100 to $1,000, depending on whether the issue is a minor wiring repair or involves replacing the DC/DC converter.
What tools are needed to troubleshoot the P305C code?
Common tools include a multimeter to check voltage, a scan tool to read live data, and basic hand tools for inspecting and repairing wiring or connectors.
Can the P305C code clear itself after a battery replacement?
In some cases, replacing the failing battery may resolve the issue and clear the code, but the underlying system should still be inspected.
Is the P305C code specific to hybrid or electric Buick models?
Yes, this code is typically associated with hybrid or electric models that use a DC/DC converter to manage electrical systems.
Discuss the causes and fixes for P305C Buick OBDII Code
Code P305C Buick comments
No comments found for this page.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
