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P105A Buick Code - Reductant Pump Low Speed

Quick Answer

The P105A Buick code refers to a Reductant Pump Low Speed error. Common causes include Faulty Reductant Pump: The most common cause of the P105A code is a malfunctioning or failing reductant pump, Wiring Issues: Electrical problems such as damaged wiring, loose connections, or corroded terminals can also trigger this code, DEF Contamination: Contaminated or low-quality DEF can clog the reductant pump or injector, leading to reduced flow rates. 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
P105A Buick indicates Reductant Pump Low Speed.
Common causes
Common causes include Faulty Reductant Pump: The most common cause of the P105A code is a malfunctioning or failing reductant pump, Wiring Issues: Electrical problems such as damaged wiring, loose connections, or corroded terminals can also trigger this code, DEF Contamination: Contaminated or low-quality DEF can clog the reductant pump or injector, leading to reduced flow rates.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 10, 2024
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Code P105A Buick Description

The P105A Buick code refers to a Reductant Pump Low Speed error. The reductant pump is a crucial component of the vehicle's emissions control system, specifically in vehicles equipped with a Selective Catalytic Reduction (SCR) system. This system helps reduce harmful emissions by injecting a urea-based solution (commonly known as Diesel Exhaust Fluid or DEF) into the exhaust stream, which reacts with harmful nitrogen oxides (NOx) to convert them into harmless nitrogen and water vapor.

OBDII Code P105A Buick - Reductant Pump Low Speed
P105A Buick Code - Reductant Pump Low Speed

Common Causes of P105A Buick

  1. Faulty Reductant Pump: The most common cause of the P105A code is a malfunctioning or failing reductant pump.
  2. Wiring Issues: Electrical problems such as damaged wiring, loose connections, or corroded terminals can also trigger this code.
  3. DEF Contamination: Contaminated or low-quality DEF can clog the reductant pump or injector, leading to reduced flow rates.
  4. Software or Calibration Issues: In some cases, software glitches or calibration errors in the SCR system can cause the reductant pump to operate at low speed.
  5. Exhaust System Blockages: Blockages in the exhaust system, such as a clogged diesel particulate filter (DPF) or SCR catalyst, can affect the reductant pump's performance.

Symptoms of P105A Buick

  1. Check Engine Light: The most common symptom associated with the P105A code is the illumination of the check engine light on the vehicle's dashboard.
  2. Reduced Performance: The vehicle may experience reduced engine performance, including decreased power and acceleration.
  3. Poor Fuel Efficiency: Inefficient DEF injection can lead to poor fuel efficiency, as the engine may not operate at optimal levels.
  4. Failed Emissions Test: A vehicle with a malfunctioning reductant pump may fail emissions tests due to increased NOx emissions.

How to Fix P105A Buick

  1. Diagnose the Issue: Use a diagnostic scan tool to retrieve the fault code and perform a thorough inspection of the reductant pump, wiring, and related components.
  2. Check DEF Quality: Verify the quality and level of DEF in the vehicle's tank, ensuring it meets the manufacturer's specifications.
  3. Test Electrical Connections: Inspect the wiring harness, connectors, and fuses associated with the reductant pump for any damage or corrosion.
  4. Replace Reductant Pump: If the pump is found to be faulty, replace it with a new OEM or high-quality aftermarket unit.
  5. Clear Codes and Test Drive: After completing the repair, clear the fault codes from the vehicle's computer, and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P105A Buick

The cost of repairing a P105A Buick code can vary depending on the specific cause of the issue and the labor rates in your area. On average, replacing a faulty reductant pump can cost between $300 and $600, including parts and labor. Additional costs may be incurred if there are wiring issues or other related components that need attention. Keep in mind that diagnostic time and labor rates at auto repair shops can fluctuate, so it's advisable to obtain quotes from multiple service providers to compare prices accurately.

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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 P105A Buick Code

1. What does the P105A code mean on a Buick?

The P105A code indicates a "Reductant Pump Low Speed" issue, meaning the reductant pump is not operating at the expected speed for the diesel exhaust fluid (DEF) system.

2. What are the symptoms of a P105A code in a Buick?

Common symptoms include the check engine light turning on, possible DEF system warnings, reduced engine performance, and failure to meet emissions standards.

3. What causes the P105A code on a Buick?

The code can be caused by a faulty reductant pump, electrical issues such as damaged wiring or connectors, a failing reductant control module, or contaminated DEF fluid.

4. Can I drive with a P105A code?

While the vehicle may still be drivable, ignoring the issue can lead to reduced engine performance and emissions compliance problems. It's best to address the issue promptly.

5. How is the P105A code diagnosed?

A technician will use an OBDII scanner to confirm the code, inspect the reductant pump, check for wiring or connection issues, and test the DEF system for proper operation.

6. How do you fix a P105A code on a Buick?

Repairs may involve replacing the reductant pump, repairing or replacing damaged wiring, cleaning out contaminated DEF fluid, or updating the reductant control module software.

7. What is the reductant pump’s role in the DEF system?

The reductant pump delivers DEF fluid to the exhaust system to reduce nitrogen oxide emissions, ensuring the vehicle meets emissions standards.

8. Can a P105A code be caused by low DEF levels?

While low DEF levels typically trigger other specific codes or warnings, maintaining proper DEF levels is essential to avoid system malfunctions.

9. How much does it cost to fix the P105A code on a Buick?

Repair costs can vary, ranging from $200 to $800 or more, depending on whether the reductant pump or other components need replacement.

10. Can a software update fix the P105A code?

In some cases, a software update for the reductant control module can resolve issues if the problem stems from incorrect system calibration or programming.

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