AutoCodes – Cadillac – P0091 Cadillac

P0091 Cadillac 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 Cadillac 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.

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Code Popularity 1,541

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

What does this mean?

What are the Possible Causes of the DTC P0091 Cadillac?

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 Cadillac?

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 Cadillac 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 P0091 Cadillac Code

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

P0091 indicates that the fuel pressure regulator control circuit is experiencing low voltage, which can affect fuel pressure regulation.

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

Symptoms may include poor engine performance, difficulty starting, stalling, decreased fuel efficiency, and an illuminated check engine light.

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

Common causes include a faulty fuel pressure regulator, damaged wiring or connectors in the control circuit, a failing fuel pump control module, or a problem with the ECM.

4. Can I drive my Cadillac with a P0091 code?

Driving with this code is not recommended, as improper fuel pressure can cause engine performance issues and may lead to further damage.

5. How do I diagnose the P0091 code in my Cadillac?

Diagnose the issue by checking the wiring and connectors in the fuel pressure regulator control circuit, testing the fuel pressure regulator, and inspecting the fuel pump control module.

6. How is the P0091 code fixed in a Cadillac?

Repairs may include repairing or replacing damaged wiring, replacing the fuel pressure regulator, fixing or replacing the fuel pump control module, or reprogramming the ECM if necessary.

7. Can a dirty fuel filter cause a P0091 code in a Cadillac?

While unlikely, a dirty or clogged fuel filter can contribute to fuel pressure issues, so itâ€™s worth inspecting as part of the diagnostic process.

8. Is P0091 a common code for Cadillacs?

P0091 is not among the most common codes but can occur in Cadillacs if there are issues with the fuel pressure regulator circuit or related components.

9. How much does it cost to fix a P0091 code on a Cadillac?

Repair costs vary depending on the cause, but replacing a fuel pressure regulator can cost $200â€“$400, while wiring repairs or module replacements can be more expensive.

10. Can a bad ECM cause the P0091 code in a Cadillac?

Yes, a malfunctioning ECM can cause the P0091 code by failing to properly control the fuel pressure regulator circuit.