AutoCodes – Buick – P105A Buick

P105A Buick Code - Reductant Pump Low Speed

Quick Answer

The reductant pump motor is controlled by the reductant control module. Common causes include Faulty Reductant Pump and Sensor Assembly, Reductant Pump and Sensor Assembly harness is open or shorted, Reductant Pump and Sensor Assembly 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: P105A Buick indicates Reductant Pump Low Speed.
Common causes: Common causes include Faulty Reductant Pump and Sensor Assembly, Reductant Pump and Sensor Assembly harness is open or shorted, Reductant Pump and Sensor Assembly 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.

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Code Popularity 410

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 Jul 24, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P105A Buick Description

The reductant pump motor is controlled by the reductant control module. The Engine Control Module (ECM) sends a command to the reductant control module via a direct wire connection. This command is converted by the reductant control module into the desired pump speed The ECM checks the state of the wire to the reductant control module for circuit continuity. The signal sent by the ECM to the reductant control module is diagnosed for open circuit, short circuit to ground, and short circuit to voltage. The Diagnostic Trouble Code (DTC) will be set when the reductant control module detects that the reductant pump rotor is stalled for greater than 5 s.

OBDII Code P105A Buick - Reductant Pump Low Speed - AutoCodes.com — P105A Buick Code - Reductant Pump Low Speed

What does this mean?

What are the Possible Causes of the DTC P105A Buick?

Faulty Reductant Pump and Sensor Assembly
Reductant Pump and Sensor Assembly harness is open or shorted
Reductant Pump and Sensor Assembly circuit poor electrical connection
Faulty Reductant Control Module

How to Fix the DTC P105A 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 P105A 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.

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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 pumpâ€™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.