AutoCodes – GMC – P2633 GMC

P2633 GMC Code - Fuel Transfer Pump Relay Control Circuit Low Voltage

Quick Answer

The Engine Control Module (ECM) enables the secondary fuel pump relay when the primary fuel tank is below approximately 50 liters (13.2 gallons) and will run until the primary tank is filled to approximately 70 liters (18.5 gallons) or until the secondary tank is empty. Common causes include Faulty Secondary Fuel Pump Relay, Secondary Fuel Pump Relay harness is open or shorted, Secondary Fuel Pump Relay 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: P2633 GMC indicates Fuel Transfer Pump Relay Control Circuit Low Voltage.
Common causes: Common causes include Faulty Secondary Fuel Pump Relay, Secondary Fuel Pump Relay harness is open or shorted, Secondary Fuel Pump Relay 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 414

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 Aug 01, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P2633 GMC Description

The Engine Control Module (ECM) enables the secondary fuel pump relay when the primary fuel tank is below approximately 50 liters (13.2 gallons) and will run until the primary tank is filled to approximately 70 liters (18.5 gallons) or until the secondary tank is empty. The ECM provides ignition positive voltage to the coil side of the fuel transfer pump relay. The ECM energizes the fuel transfer pump relay, which applies power to the fuel transfer pump.
The control module monitors the voltage on the fuel transfer pump relay control circuit. If the control module detects an incorrect voltage on the fuel transfer pump relay control circuit, a fuel transfer pump relay control Diagnostic Trouble Code (DTC) sets.

OBDII Code P2633 GMC - Fuel Transfer Pump Relay Control Circuit Low Voltage - AutoCodes.com — P2633 GMC Code - Fuel Transfer Pump Relay Control Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P2633 GMC?

Faulty Secondary Fuel Pump Relay
Secondary Fuel Pump Relay harness is open or shorted
Secondary Fuel Pump Relay circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P2633 GMC?

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 P2633 GMC 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 P2633 GMC code?

Need more information on how to fix the P2633 GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

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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 P2633 GMC Code

1. What are the common symptoms of OBDII code P2633 GMC (Fuel Transfer Pump Relay Control Circuit Low Voltage)?

- Common symptoms include difficulty starting the vehicle, reduced engine performance, and illuminated check engine light.

2. What are the possible causes of OBDII code P2633 GMC?

- Possible causes include a faulty fuel transfer pump relay, wiring issues in the relay control circuit, or a malfunctioning powertrain control module (PCM).

3. How can I diagnose the cause of OBDII code P2633 GMC?

- Diagnose the code by inspecting the fuel transfer pump relay and related wiring for any damage or loose connections. Use a multimeter to test the relay's functionality.

4. Can I drive my vehicle with OBDII code P2633 GMC?

- It is not recommended to drive the vehicle with this code present, as it can lead to further damage to the fuel system and affect engine performance.

5. How can I repair OBDII code P2633 GMC?

- Repair options include replacing the faulty fuel transfer pump relay, repairing any damaged wiring, or reprogramming the PCM if necessary.

6. Is it safe to reset the check engine light after fixing OBDII code P2633 GMC?

- Yes, once the issue causing the code has been resolved, it is safe to reset the check engine light using an OBDII scanner.

7. Are there any preventive measures to avoid OBDII code P2633 GMC in the future?

- Regularly inspecting and maintaining the fuel transfer pump relay and related wiring can help prevent this code from occurring in the future.

8. Can a DIY enthusiast fix OBDII code P2633 GMC?

- Depending on your skill level and access to tools, a DIY enthusiast may be able to diagnose and repair this code. However, professional assistance is recommended for complex electrical issues.

9. Will OBDII code P2633 GMC affect fuel efficiency?

- Yes, this code can affect fuel efficiency due to improper fuel transfer pump relay operation, leading to inefficient fuel delivery to the engine.

10. How long does it typically take to repair OBDII code P2633 GMC?

- The repair time can vary depending on the exact cause of the code and the extent of the repairs needed. It can take anywhere from 1-3 hours to fix this issue.