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Engine-Codes – GMC – U18A2 GMC

U18A2 GMC Code - Lost Communication with Fuel Pump Driver Control Module

Quick Answer

The U18A2 diagnostic trouble code (DTC) for GMC vehicles indicates that there is a communication problem between the vehicle's engine control module (ECM) and the fuel pump driver control module. Common causes include Wiring issues or loose connections, Faulty fuel pump driver control module, Corrosion or water damage in the electrical system. 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
U18A2 GMC indicates Lost Communication with Fuel Pump Driver Control Module.
Common causes
Common causes include Wiring issues or loose connections, Faulty fuel pump driver control module, Corrosion or water damage in the electrical system.
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 Aug 19, 2024
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Code U18A2 GMC Description

The U18A2 diagnostic trouble code (DTC) for GMC vehicles indicates that there is a communication problem between the vehicle's engine control module (ECM) and the fuel pump driver control module. The fuel pump driver control module is responsible for regulating the fuel pump's operation, ensuring that the correct amount of fuel is delivered to the engine at all times. When communication is lost between these two modules, it can lead to issues with fuel delivery, potentially causing the vehicle to stall or have difficulty starting.

OBDII Code U18A2 GMC - Lost Communication with Fuel Pump Driver Control Module
U18A2 GMC Code - Lost Communication with Fuel Pump Driver Control Module

Common Causes of U18A2 GMC

  1. Wiring issues or loose connections
  2. Faulty fuel pump driver control module
  3. Corrosion or water damage in the electrical system
  4. Electrical shorts or blown fuses
  5. Poor ground connections

Symptoms of U18A2 GMC

  1. Engine stalling or rough idling
  2. Difficulty starting the vehicle
  3. Decreased fuel efficiency
  4. Engine misfires
  5. Hesitation or lack of power during acceleration

How to Fix U18A2 GMC

  1. Check and repair any damaged or loose wiring connections between the ECM and the fuel pump driver control module.
  2. Inspect the fuel pump driver control module for any signs of malfunction and replace if necessary.
  3. Verify and repair any corrosion or water damage in the electrical system.
  4. Test and replace any blown fuses or repair electrical shorts.
  5. Ensure all ground connections are secure and functioning properly.

Cost to Fix U18A2 GMC

The typical repair costs for addressing a lost communication issue with the fuel pump driver control module can range from $200 to $500, including parts and labor. However, it's important to note that specific diagnosis time and labor rates can vary depending on the location, vehicle make and model, and engine type. It's recommended to contact local auto repair shops for a more accurate estimate based on individual circumstances.

What does this mean?

Tech Notes for U18A2 GMC

There is a Factory Service Bulletin for the following GMC Models:

- 2014-2018 GMC Sierra
- 2015-2018 GMC Yukon
- 2015-2018 GMC Yukon XL

If the Diagnostic Trouble Codes (DTC) P2635, U0074, and/or U18A2 are set, it may be found that the actual fuel pressure (low-pressure system) will be reading substantially higher than desired fuel pressure, in this case, the cause of the problem is a loss of communication between Engine Control Module (ECM) and Fuel Pump Control Module (FPCM).

- Diagnose for any communication DTCs set (U0074 would take priority over U18A2 if both set) before addressing DTC P2635.
- If DTC P2635 is not resolved by correcting the communication DTCs, only then should diagnose the DTC P2635.
- It has been found that a communication issue between the FPCM and ECM can potentially induce DTC P2635 and result in a pressure differential between actual and desired fuel system pressures.
- If the actual fuel pressure is substantially higher than desired (10 psi / 70 kPa or more), replacement of the fuel pump control module or fuel system components typically will not resolve this issue.
- If the actual fuel pressure is substantially lower than desired (10 psi / 70 kPa or more), this Factory Service Bulletin would NOT apply. It would be recommended to diagnose low actual fuel pressure.

Need more information about the U18A2 GMC code?

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Information for Specific GMC Models

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 U18A2 GMC Code

1. What are the common symptoms of OBDII code U18A2 GMC (Lost Communication with Fuel Pump Driver Control Module)?

- Common symptoms include engine stalling, rough idle, difficulty starting the vehicle, and the fuel pump not functioning properly.

2. What are the possible causes of OBDII code U18A2 GMC?

- Possible causes include a faulty fuel pump driver control module, damaged wiring or connectors, a blown fuse, or a problem with the fuel pump itself.

3. How can I diagnose the OBDII code U18A2 GMC issue?

- To diagnose this issue, you can use a diagnostic scanner to retrieve the trouble codes and perform a thorough inspection of the fuel pump driver control module, wiring, connectors, and fuse.

4. What are some repair tips for resolving OBDII code U18A2 GMC?

- Repair tips include checking and replacing any damaged wiring or connectors, testing and replacing the fuel pump driver control module if necessary, and ensuring that the fuse related to the fuel pump is in good condition.

5. Can OBDII code U18A2 GMC be safely driven with?

- It is not recommended to drive the vehicle with this code present, as it can lead to potential issues with fuel delivery and engine performance.

6. How much does it typically cost to repair OBDII code U18A2 GMC?

- The cost of repairing this code can vary depending on the extent of the issue and the specific repairs needed. It is recommended to consult with a mechanic for an accurate estimate.

7. Can I reset the OBDII code U18A2 GMC myself?

- You can attempt to reset the code using an OBDII scanner, but it is important to address the underlying issue causing the code to prevent it from reoccurring.

8. Will disconnecting the battery reset the OBDII code U18A2 GMC?

- Disconnecting the battery may reset the code temporarily, but it is not a guaranteed solution. It is best to diagnose and repair the issue causing the code.

9. How urgent is it to address OBDII code U18A2 GMC?

- It is important to address this code promptly to prevent potential fuel delivery issues and further damage to the vehicle's components.

10. Can a DIY enthusiast repair OBDII code U18A2 GMC at home?

- Depending on the DIY enthusiast's skill level and access to tools, some repairs related to this code, such as checking and replacing fuses or connectors, may be possible at home. However, more complex repairs may require professional assistance.

Discuss the causes and fixes for U18A2 GMC OBDII Code

Submit a New Comment

  • No warning no light went to church on Sunday canyon would not start on Monday. My code reader pulled U18A2

    Reply to Comment

    • Can you share the model and year of your vehicle? This helps in providing specific guidance since U18A2 is a manufacturer-specific code.

      Did you notice any unusual behavior before it stopped working? For example, was the vehicle cranking but not starting, or was it completely unresponsive?

      U18A2 typically relates to a communication issue between the vehicle's modules. Here are some steps to investigate the issue:

      1. Inspect Battery and Connections: Ensure the battery is fully charged and the terminals are clean and secure. Low voltage can trigger communication-related codes.

      2. Check for Wiring Issues: Inspect the wiring and connectors leading to the modules. Look for damage, corrosion, or loose connections.

      3. Scan All Modules: Use a scanner capable of reading manufacturer-specific codes to check for additional codes in related modules like the ECM, BCM, or TCM.

      4. Reset the System: Disconnect the battery for about 10 minutes, then reconnect it. This can reset module communication and clear temporary glitches.

      Reply to Comment