U0109 on 2024-2025 Jeep Wrangler: Lost Communication With Fuel Pump Control Module Fixes

What's Unique About the 2024-2025 Jeep WRANGLER

For the 2024-2025 Jeep Wrangler (JL generation), the U0109 code is specifically cited in Technical Service Bulletin #23-019-25 REV. B. This TSB groups U0109 with a host of other seemingly unrelated codes, suggesting that a single underlying issue (like a software glitch or broad electrical fault) could be the cause, and a dealer-level inspection or reflash may be required. Forum discussions for the JL Wrangler highlight that wiring and connector problems are a common real-world cause. One owner on JLWranglerForums.com pinpointed the issue to a broken pin on a module under the main fuse box, which was damaged during an auxiliary battery change. 🎬 See how a bad auxiliary battery can cause no-start issues. This underscores the importance of checking for physical damage to harnesses and connectors, especially after other services have been performed near the battery or fuse box. Another potential failure point on JL/JT models is the CAN Bus Star Connector located behind the glove box, which can fail 🎬 Watch: How a star connector failure causes multiple service lights. due to heat and cause widespread communication errors.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Engine cranks but will not start.
• Engine stalls unexpectedly while driving.
• Hard crank followed by a brief start, then stumbling and stalling.
• Rough running, hesitation, or lack of power.
• Check Engine Light is illuminated.
• The electric fuel pump may not make its typical priming sound when the key is turned to the 'ON' position.
• Service messages for the Electronic Throttle Control or Auto Start/Stop system may appear immediately after stalling.
• Dashboard lights up with multiple warnings (Christmas tree effect), including for ABS, Traction Control, and 4WD systems, if the failure is at a central network point like the Star Connector.

Most Likely Causes

1. Wiring Harness or Connector Damage 🔴 High Probability Wiring can be susceptible to damage from road debris, moisture, or chafing. A specific, owner-confirmed failure point on the JL Wrangler is a broken pin on a module connector located under the main fuse box, which can be damaged during auxiliary battery service. Connectors can also suffer from corrosion or pushed-out pins.
   How to confirm: Visually inspect the wiring harness between the PCM and the FPCM for any signs of damage, chafing, or corrosion. Pay close attention to the connectors at both modules and the large connectors under the fuse box. Use a digital multimeter to check for continuity on the CAN bus wires.
   Typical fix: Repair the damaged section of the wire or replace the faulty connector. In the case of the broken pin under the fuse box, the module or connector may need replacement.
   Est. part cost: $10-$100
2. Failed Fuel Pump Control Module (FPCM) 🟡 Medium Probability → Shop Fuel Pump Electronic modules can fail due to internal component breakdown, heat, or vibration. While less common than wiring issues, a faulty FPCM is a frequent cause for U0109.
   How to confirm: After confirming the wiring, power, and ground to the FPCM are all good, the module itself becomes the primary suspect. A professional scan tool may be able to communicate directly with the FPCM; if it cannot, the module has likely failed.
   Typical fix: Replace the Fuel Pump Control Module. The new module may require programming by a dealer or a properly equipped independent shop.
   Est. part cost: $110-$170
3. Loss of Power or Ground to the FPCM 🟡 Medium Probability A blown fuse or a corroded ground connection can prevent the FPCM from powering on, leading to a communication loss code. Forum users have reported that a bad connection at the fuel pump fuse can cause intermittent no-start conditions.
   How to confirm: Check the fuse designated for the FPCM. On the JL Wrangler, this is fuse F04 (20A Micro fuse) in the engine bay fuse box. Use a multimeter to verify that the FPCM is receiving battery voltage on its power wire and has a solid connection to ground on its ground wire.
   Typical fix: Replace the blown fuse or clean and secure the ground connection. If the fuse terminal itself is loose or burnt, the fuse box may require repair or replacement.
   Est. part cost: $1-$20

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) While rare, the PCM itself can fail, causing it to be unable to communicate with other modules. This should be considered only after all other possibilities have been exhausted, as it is an expensive and complex repair.
• CAN Bus Network Fault (Star Connector): A fault elsewhere on the CAN bus network, such as a short in the wiring for a different module or a bad termination resistor, can disrupt all communication, including that with the FPCM. On JL/JT models, the CAN Bus Star Connector block behind the glove box is a known failure point that can cause intermittent, widespread communication codes due to poor internal solder joints.
🎬 Watch: Step-by-step guide to fixing the CAN-C star connector gremlin.

Diagnosis Steps

1. Scan for all DTCs. Note any other communication (U-codes) or circuit (P-codes) that are present, especially P025A.
2. Check fuse F04 (20A Yellow Micro) in the engine bay fuse box. Inspect for a blown fuse and ensure the terminals have a tight grip. A loose connection here is a known issue.
3. Locate the FPCM. On the JL Wrangler, it is mounted on the driver's side frame rail, near the fuel tank, and is accessible from underneath the vehicle.
4. Visually inspect the FPCM connector and its wiring harness for any obvious signs of damage, corrosion, or loose connections.
5. Inspect the large connectors on the underside of the engine bay fuse box, especially if the auxiliary battery has been recently serviced. Look for bent or broken pins.
6. Using a multimeter, verify that the FPCM is receiving battery voltage (typically 11.5-12.5V) on its power supply pin and has a good, clean ground connection.
7. Test the CAN bus wiring between the PCM and the FPCM. Check for continuity on both the CAN High and CAN Low wires. With the battery disconnected, check the resistance between the two CAN wires; it should be approximately 60 ohms if the network is intact.
8. If wiring, power, and ground are all confirmed to be good, the Fuel Pump Control Module is the most likely failed component.
9. If replacing the FPCM does not resolve the issue, the problem may lie with a more complex network fault, such as a faulty CAN Star Connector behind the glove box, or the Powertrain Control Module (PCM), though this is uncommon.

Parts You'll Likely Need

• Fuel Pump Control Module (FPCM) (OEM #68434538AA) — If the wiring, power, and ground are intact, the module itself is the next logical point of failure causing the communication loss.
  Trusted brands: Mopar
  OEM price range: $110-$170
  Aftermarket price range: $90-$150

Related Codes That Often Appear With This One

• P025A — This code for 'Fuel Pump Module Control Circuit Open' often appears with U0109, strongly indicating an electrical fault in the FPCM's circuit or the module itself.
• P0528 — A user on the JL Wrangler Forums reported this code for 'Fan Speed Sensor Circuit' appeared at the same time as U0109, suggesting a possible shared power, ground, or network issue.
• P02EF — Mentioned in TSB #23-019-25 REV. B alongside U0109, this code relates to cylinder injector performance, which can be affected by inconsistent fuel delivery.
• P0330 — Also listed in TSB #23-019-25 REV. B, this knock sensor code can be triggered by engine performance issues stemming from the fuel system problem.

Technical Service Bulletins (TSBs) & Recalls

• 23-019-25 REV. B: Mentions U0109 - Lost Communication With Fuel Pump Control Module in a list of potential diagnostic trouble codes for the 2024 model year that may trigger a Malfunction Indicator Lamp (MIL).

Platform-Specific Known Issues

• A known issue documented in TSB #23-019-25 REV. B lists U0109 among a group of codes that can occur on 2024 models, sometimes indicating a need for a broader diagnostic approach or software update.
• A user on JLWranglerForums.com reported that code U0109 was ultimately caused by a broken pin on a module under the fuse box, which was damaged during an auxiliary battery replacement.
• Another owner on JLWranglerForums.com reported a brand new 2025 Wrangler threw codes U0109 and P025A with less than 300 miles, resulting in a crank/stall condition that temporarily resolved itself.
• A loose connection at the F04 fuel pump fuse in the main fuse box has been identified by owners as a cause for intermittent no-start and communication codes.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: ~60 Ω (Ohms) between CAN-C High and CAN-C Low pins at the OBD-II port (pins 6 & 14) with the battery disconnected.. Failure: A reading of ~120 Ω indicates an open circuit or a break in one of the bus lines or a faulty terminating resistor. A reading significantly lower than 60 Ω suggests a short between the CAN High and Low wires.
• CAN Bus Voltage (Key On, Engine Off) — expected: CAN High (Pin 6): Fluctuating 2.5V to 3.5V (multimeter average ~2.6V). CAN Low (Pin 14): Fluctuating 1.5V to 2.5V (multimeter average ~2.4V).. Failure: Voltages that are stuck high, low, or at 0V indicate a short to power, short to ground, or an open circuit.
• FPCM Power Supply Voltage — expected: 11.5V - 12.5V at the FPCM power supply pin with the key in the 'ON' position.. Failure: Low or no voltage indicates a problem with the fuse, relay, or wiring supplying power to the module.

Scan Tool Commands That Help

• wiTECH 2.0: Network Topology View — This is the first screen to check. It provides a color-coded overview of all modules on the network. A gray or red FPCM icon immediately confirms a communication issue.
• wiTECH 2.0: ECU View > FPCM > Actuators — After confirming power and ground to the FPCM, a technician can use this function to command the fuel pump to turn on. If the pump does not activate despite good wiring, it strongly suggests the FPCM itself has failed.
• wiTECH 2.0 / J2534 Application: Reprogram ECU / Flash Module — If a TSB indicates a software update is available to fix a condition causing U0109, this function is used to load the new software onto the PCM or FPCM.

Wiring & Ground Locations

• CAN Star Connector (IP) — Located behind the glove box, mounted to a plastic rail. The glove box must be lowered or removed for access.. This is a central junction for many CAN bus modules. A common failure point on JL/JT models, bad solder joints inside this connector can cause intermittent loss of communication to multiple modules, including the FPCM. Wiggling the wires to this connector while the fault is active may temporarily restore function, confirming it as the problem.
• G901A / G902A — Main battery ground points located on the body near the battery in the engine compartment.. These are primary ground points for the entire vehicle's electrical system. Corrosion or a loose connection here can cause a wide range of unpredictable electrical issues, including module communication failures.
• FPCM Connector — On the Fuel Pump Control Module, which is mounted to the driver's side frame rail near the fuel tank.. This is the direct connection point for the FPCM's power, ground, and CAN bus wires. It should be inspected for corrosion, moisture intrusion, or pushed-out pins.
• Fuse F04 — In the Power Distribution Center (main fuse box) in the engine bay. It is a 20A Micro fuse.. This fuse supplies power to the Fuel Pump Motor and the FPCM. A blown fuse or, more commonly, a loose terminal connection at this fuse location will cut power to the module and cause a U0109 code.

Real Owner Repair Stories

• JLWranglerForums.com user (2019 Jeep Wrangler JLU) — Dashboard would 'freak out' with every possible error code, sometimes causing the engine to die. Errors were all CAN-C data bus related.
  ❌ Tried (didn't work) Vehicle spent two months at the dealer with no resolution.
  ✅ What actually fixed it The owner replaced the CAN Bus Star Connector (Part No. 68321746AA) located behind the glove box, which resolved all communication errors.
• JLWranglerForums.com user (Jeep Wrangler JL) — Engine dying without warning while driving, followed by a no-start or rough idle and stall. Codes U0109 and P0528 were present.
  ❌ Tried (didn't work) Dealer replaced the Fuel Pump Control Module, but the vehicle stalled again 17 miles later.
  ✅ What actually fixed it A different user in the same thread found the cause on their vehicle to be a broken pin on a module connector under the main fuse box, which was damaged during an auxiliary battery change.

OEM Part Supersession History

• 68321746AA → 68230877AA — The original 20-way CAN Star Connector is often superseded by a 13-way connector in newer models. They are functionally interchangeable.
  Heads up: The connectors are interchangeable, but a technician must transfer the individual wire plugs from the old connector to the new one. The order does not matter, except for the main power feed which is a different size.