AutoCodes – Cadillac – U18A2 Cadillac

U18A2 Cadillac 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 Cadillac 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 3,416

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 Cadillac 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 Cadillac - Lost Communication with Fuel Pump Driver Control Module - AutoCodes.com — U18A2 Cadillac Code - Lost Communication with Fuel Pump Driver Control Module

What does this mean?

What are the Possible Causes of the DTC U18A2 Cadillac?

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 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 does this mean?

Code Tech Notes

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

- 2015-2018 Cadillac Escalade

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 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 U18A2 Cadillac Code

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

Symptoms may include difficulty starting the vehicle, engine stalling, loss of power while driving, and illuminated check engine light.

2. What are some possible causes of the U18A2 code in a Cadillac?

Potential causes can include a faulty fuel pump driver control module, damaged wiring or connectors, a blown fuse, or a malfunctioning powertrain control module.

3. How can I diagnose the U18A2 trouble code in my Cadillac?

Diagnosis typically involves using a diagnostic scanner to retrieve the code, checking the fuel pump driver control module for communication issues, inspecting wiring and connectors for damage, and testing relevant fuses.

4. Is it safe to continue driving with the U18A2 code present in my Cadillac?

It is not recommended to drive the vehicle with this code present, as it can lead to potential issues like stalling or loss of power, which can pose safety risks.

5. Can I repair the U18A2 code in my Cadillac myself?

While some DIY enthusiasts may attempt to address this code themselves by checking connections and fuses, it is recommended to have a professional diagnose and repair the issue due to the complexity of the fuel pump control system.

6. How much does it typically cost to repair the U18A2 code in a Cadillac?

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

7. Will resetting the trouble codes make the U18A2 code disappear permanently?

Simply resetting the trouble codes may temporarily clear the check engine light, but if the underlying issue causing the U18A2 code is not addressed, the code is likely to reappear.

8. Can a bad fuel pump cause the U18A2 code to trigger in a Cadillac?

While a faulty fuel pump may not directly trigger the U18A2 code, it can lead to communication issues with the fuel pump driver control module, which in turn can cause the code to be stored in the system.

9. Are there any preventive maintenance steps to avoid the U18A2 code in a Cadillac?

Regularly inspecting and maintaining the fuel pump system, checking wiring and connectors for damage, and addressing any issues promptly can help prevent the occurrence of the U18A2 trouble code.

10. How urgent is it to address the U18A2 code in a Cadillac?

It is advisable to address the U18A2 code promptly to prevent potential drivability issues and ensure the vehicle's safe operation. Delaying repairs can lead to further damage and safety risks.