AutoCodes – Mercury – U0109 Mercury

U0109 Mercury Code - Lost Communication With Fuel Pump Control Module

Quick Answer

The Powertrain Control Module (PCM) monitors the Fuel Pump Monitor (FPM) circuit for the presence of a duty cycled signal. Common causes include Fuel pump monitor circuit open or short to ground, Fuel pump monitor circuit short to voltage, Damaged Inertia Fuel Shutoff (IFS) switch (if equipped). 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: U0109 Mercury indicates Lost Communication With Fuel Pump Control Module .
Common causes: Common causes include Fuel pump monitor circuit open or short to ground, Fuel pump monitor circuit short to voltage, Damaged Inertia Fuel Shutoff (IFS) switch (if equipped).
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 1,509

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 Mar 29, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U0109 Mercury Description

The Powertrain Control Module (PCM) monitors the Fuel Pump Monitor (FPM) circuit for the presence of a duty cycled signal. If the FPM circuit is fixed at a low or high voltage, the PCM begins to increment a counter. The test fails when the PCM is still not detecting a duty cycled signal on the FPM circuit after a calibrated amount of time.

OBDII Code U0109 Mercury - Lost Communication With Fuel Pump Control Module - AutoCodes.com — U0109 Mercury Code - Lost Communication With Fuel Pump Control Module

What does this mean?

What are the Possible Causes of the DTC U0109 Mercury?

Fuel pump monitor circuit open or short to ground
Fuel pump monitor circuit short to voltage
Damaged Inertia Fuel Shutoff (IFS) switch (if equipped)
Damaged fuel pump control module relay

How to Fix the DTC U0109 Mercury?

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 U0109 Mercury 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 U0109 Mercury code?

Need more information on how to fix the U0109 Mercury 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 U0109 Mercury Code

1. What does the OBDII code U0109 mean for a Mercury vehicle?

U0109 indicates a lost communication with the Fuel Pump Control Module (FPCM), meaning the module is not responding to signals from the powertrain control module (PCM).

2. What are the common symptoms of code U0109 in a Mercury?

Symptoms include engine stalling, difficulty starting the vehicle, reduced fuel efficiency, or the engine not starting at all.

3. What causes the U0109 code to appear in a Mercury vehicle?

Common causes include a faulty Fuel Pump Control Module, damaged wiring or connectors, issues with the CAN bus network, or a failing PCM.

4. Can a bad fuel pump cause the U0109 code in a Mercury?

While the fuel pump itself may not directly trigger the code, problems with the Fuel Pump Control Module or its communication could affect the pump's operation.

5. How can I diagnose the U0109 code in my Mercury?

Start by inspecting the wiring and connectors for damage or corrosion, check the CAN bus network for continuity, and test the FPCM using a scan tool capable of reading live data.

6. Is it safe to drive a Mercury with the U0109 code?

Driving with this code is not recommended as it may lead to engine stalling or failure to start, potentially leaving you stranded.

7. How do I fix the U0109 code on my Mercury?

Repairs may include replacing or repairing damaged wiring, connectors, or the Fuel Pump Control Module, and ensuring the CAN bus network is functioning properly.

8. Can a software issue cause the U0109 code in a Mercury?

Yes, outdated or corrupted PCM or FPCM software can sometimes cause communication errors that trigger this code.

9. How much does it cost to repair the U0109 code on a Mercury?

Repair costs vary depending on the cause, but replacing the Fuel Pump Control Module typically ranges from $300 to $800, excluding labor.

10. Do I need a professional mechanic to fix the U0109 code on my Mercury?

While some issues like inspecting wiring can be done by a DIYer, diagnosing and repairing CAN bus communication problems or module replacements often require professional tools and expertise.