AutoCodes – GMC – U18A2 2018 GMC Sierra

U18A2 2018 GMC Sierra Code - Lost Communication with Fuel Pump Driver Control Module

Quick Answer

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Fuel Pump Driver Control Module, Fuel Pump Driver Control Module harness is open or shorted, Fuel Pump Driver Control Module 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: U18A2 2018 GMC Sierra indicates Lost Communication with Fuel Pump Driver Control Module.
Common causes: Common causes include Faulty Fuel Pump Driver Control Module, Fuel Pump Driver Control Module harness is open or shorted, Fuel Pump Driver Control Module 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 682

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 Apr 14, 2023

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code U18A2 2018 GMC Sierra Description

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the devices. The devices have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver device as an availability indication of the transmitter device. Each message contains the identification number of the transmitter device. The Diagnostic Trouble Code (DTC) will set a supervised periodic message that includes the transmitter device availability that has not been received.

OBDII Code U18A2 2018 GMC Sierra - Lost Communication with Fuel Pump Driver Control Module - AutoCodes.com — U18A2 2018 GMC Sierra Code - Lost Communication with Fuel Pump Driver Control Module

What does this mean?

What are the Possible Causes of the DTC U18A2 2018 GMC Sierra?

Faulty Fuel Pump Driver Control Module
Fuel Pump Driver Control Module harness is open or shorted
Fuel Pump Driver Control Module circuit poor electrical connection

How to Fix the DTC U18A2 2018 GMC Sierra?

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 does this mean?

Code Tech Notes

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

- 2014-2018 Chevrolet Silverado
- 2015-2018 Chevrolet Suburban
- 2015-2018 Chevrolet Tahoe

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.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U18A2 2018 GMC Sierra 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 U18A2 2018 GMC Sierra code?

Need more information on how to fix the U18A2 2018 GMC Sierra code? Get Access to Factory Service Manuals

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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 U18A2 2018 GMC Sierra Code

1. What are the common symptoms of OBDII code U18A2 in a 2018 GMC Sierra indicating a lost communication with the Fuel Pump Driver Control Module?

- Common symptoms include issues starting the vehicle, stalling, rough idling, and a non-functioning fuel pump.

2. What are the potential causes of the OBDII code U18A2 in a 2018 GMC Sierra?

- The code U18A2 can be triggered by a faulty fuel pump driver control module, damaged wiring or connectors, or a malfunctioning powertrain control module.

3. How can I diagnose the underlying issue causing the OBDII code U18A2 in my 2018 GMC Sierra?

- Diagnosis typically involves checking the wiring and connectors for damage, testing the fuel pump driver control module for functionality, and scanning the vehicle's computer for any related trouble codes.

4. Is it safe to continue driving my 2018 GMC Sierra with the U18A2 code indicating a lost communication with the Fuel Pump Driver Control Module?

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

5. How can I repair the lost communication with the Fuel Pump Driver Control Module issue in my 2018 GMC Sierra?

- Repairing this issue may involve replacing the fuel pump driver control module, repairing damaged wiring or connectors, or reprogramming the powertrain control module.

6. Can a DIY enthusiast tackle the repair of the U18A2 code in a 2018 GMC Sierra?

- While some basic troubleshooting steps can be performed by DIY enthusiasts, the complexity of the repair may require professional assistance, especially when dealing with electronic modules.

7. Are there any preventive measures to avoid encountering the U18A2 code in a 2018 GMC Sierra in the future?

- Regular maintenance checks, including inspecting the fuel system components and ensuring proper electrical connections, can help prevent issues leading to the U18A2 code.

8. Will resetting the trouble codes clear the U18A2 code in a 2018 GMC Sierra?

- Resetting the trouble codes may temporarily clear the U18A2 code, but if the underlying issue causing the communication loss is not addressed, the code is likely to reappear.

9. How much can I expect to pay for the repair of the U18A2 code in a 2018 GMC Sierra at a dealership or mechanic?

- The cost of repair can vary depending on the exact cause of the issue, but it's advisable to budget for diagnostic fees, parts replacement, and labor costs, which can range from a few hundred to over a thousand dollars.

10. Can a weak or failing battery cause the U18A2 code to appear in a 2018 GMC Sierra?

- Yes, a weak or failing battery can sometimes lead to communication errors between modules in the vehicle, including the Fuel Pump Driver Control Module, triggering the U18A2 code.