AutoCodes – Buick – P0091 Buick

P0091 Buick Code - Fuel Pressure Regulator Control Circuit Low Voltage

Quick Answer

High-pressure fuel is regulated by the high-pressure fuel pump actuator, which is a part of the high-pressure fuel pump. Common causes include Faulty High-Pressure Fuel Pump, High-Pressure Fuel Pump harness is open or shorted, High-Pressure Fuel Pump electrical circuit poor 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: P0091 Buick indicates Fuel Pressure Regulator Control Circuit Low Voltage.
Common causes: Common causes include Faulty High-Pressure Fuel Pump, High-Pressure Fuel Pump harness is open or shorted, High-Pressure Fuel Pump electrical circuit poor 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 1,415

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 Jun 24, 2021

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 P0091 Buick Description

High-pressure fuel is regulated by the high-pressure fuel pump actuator, which is a part of the high-pressure fuel pump. The high-pressure fuel pump actuator is a solenoid valve. The Engine Control Module (ECM) provides battery voltage on the actuator high control circuit and ground on the actuator low control circuit. Both circuits are controlled through output drivers within the ECM. When deactivated, both drivers are disabled. When activated, the high control circuit driver energizes the high-pressure fuel pump actuator, and the low control circuit driver Pulse-Width Modulates (PWM) the low control circuit to the ground. The ECM monitors the voltage on the circuits to detect a failure. The Diagnostic Trouble Code (DTC) will set if the ECM detects a short to ground in the high-pressure fuel pump actuator low control circuit.

OBDII Code P0091 Buick - Fuel Pressure Regulator Control Circuit Low Voltage - AutoCodes.com — P0091 Buick Code - Fuel Pressure Regulator Control Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P0091 Buick?

Faulty High-Pressure Fuel Pump
High-Pressure Fuel Pump harness is open or shorted
High-Pressure Fuel Pump electrical circuit poor connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P0091 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 P0091 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 P0091 Buick code?

Need more information on how to fix the P0091 Buick code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0091 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 P0091 Buick Code

1. What does the OBDII code P0091 mean for a Buick?

Code P0091 indicates a low voltage issue in the fuel pressure regulator control circuit, which can affect fuel pressure delivery to the engine.

2. What are the common symptoms of P0091 in a Buick?

Symptoms include poor engine performance, difficulty starting, reduced fuel efficiency, rough idling, and, in some cases, the engine stalling.

3. What causes the P0091 code to appear in a Buick?

Common causes include a faulty fuel pressure regulator, damaged wiring or connectors in the control circuit, a failing fuel pump, or a defective powertrain control module (PCM).

4. Can I drive my Buick with the P0091 code?

Driving with this code is not recommended, as it can lead to poor engine performance, difficulty starting, or stalling, potentially leaving you stranded.

5. How do I diagnose the P0091 code on my Buick?

Start by inspecting the wiring and connectors in the fuel pressure regulator circuit for damage or corrosion. Then test the fuel pressure regulator, fuel pump, and voltage supply to the circuit.

6. What tools are needed to fix the P0091 code on a Buick?

Youâ€™ll need an OBDII scanner, a multimeter to check voltages, and potentially specialized tools to access and replace the fuel pressure regulator or pump.

7. How much does it cost to fix the P0091 code on a Buick?

Repair costs can vary, but replacing a fuel pressure regulator typically costs $150-$400, while addressing wiring or connector issues may cost less if minor.

8. Can a bad fuel pump cause the P0091 code in a Buick?

Yes, a failing fuel pump can cause low voltage in the fuel pressure regulator control circuit, triggering the P0091 code.

9. Is the P0091 code specific to certain Buick models?

This code can appear on any Buick model equipped with an OBDII system, but the exact symptoms and fixes may vary slightly by vehicle.

10. How can I prevent the P0091 code from recurring?

Regularly inspect and maintain your fuel system, ensure wiring and connectors are in good condition, and use high-quality fuel to avoid clogging or damaging components.