Code
U0109
Generic
U — Network/User
Lost Communication With Fuel Pump Control Module A
Views:
UK: 25
EN: 100
RU: 52
AI status
Completed
Completed
100%
Causes
- Fuel Pump Control Module (FPCM) failure
- Open, short, or high-resistance wiring between FPCM and network
- Corroded or loose connector at FPCM or harness
- Blown fuse or faulty fuel pump relay supplying FPCM
- Loss of module ground or supply voltage
- Faulty or missing CAN/LIN bus termination or bus short to battery/ground
Symptoms
- No start or extended crank (fuel pump not running)
- No prime when key is cycled
- Engine may stall or run intermittently
- Check Engine light / MIL illuminated
- Other modules report related U-codes or bus communication errors
- Fuel pump relay clicking or no audible pump operation
What to check
- Connect a professional scan tool and confirm U0109 and any related U-codes or freeze frame data
- Check battery voltage and health (should be ~12.4–14.5 V with key on/engine running)
- Inspect fuses and relays for FPCM and fuel pump circuit
- Visually inspect connectors and harness at FPCM, in-tank pump, and PCM for corrosion, damage, or loose pins
- Check for other modules that have lost communication (helps narrow bus or local fault)
- Perform wiggle/torque test on harness while monitoring communication and DTC status
Signal parameters
- Battery/ignition supply to FPCM: ~9–16 V (key on)
- Module ground continuity: low resistance, typically
- CAN bus idle (recessive) voltage: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (nominal)
- CAN dominant voltages: CAN_H ≈ 3.5–4.0 V, CAN_L ≈ 1.0–1.5 V during active bits
- Expected CAN bus differential voltage (dominant): ~2.0 V
- Termination resistance (two 120 Ω in parallel on bus) ≈ 60 Ω across CAN_H–CAN_L for a single network
Diagnostic algorithm
- Verify DTC: Connect a scan tool, record freeze frame and any additional U-codes. Attempt to communicate directly with the FPCM via tool.
- Check power/ground: With key ON, measure supply voltage at FPCM power pin and verify a good ground reference. Repair any open or low-voltage circuits.
- Inspect connectors/harness: Visually and physically inspect FPCM and in-tank pump connectors for corrosion, bent pins, or water intrusion. Repair or replace as needed.
- Check fuses/relays: Verify relevant fuses/relays for FPCM and fuel pump circuit are present and functioning. Replace faulty items.
- Verify network signals: Using a multimeter or oscilloscope, measure CAN_H and CAN_L at the FPCM connector with key ON. Confirm idle and dominant voltages and check for excessive noise or shorts to power/ground.
- Check continuity and resistance: With power removed, check continuity of CAN_H/CAN_L wiring back to the PCM and measure resistance across the bus for correct termination (~60 Ω).
- Isolate the circuit: If wiring is suspected, disconnect FPCM and inspect whether removing it clears bus errors or allows other modules to communicate. Trace/repair short or open circuits as found.
- Test under load/drive cycle: After repair, clear codes and cycle ignition; verify FPCM communication returns and that the fuel pump primes and operates normally.
- Module replacement: If wiring, power, and bus are verified good and communication still fails, consider replacing FPCM or performing module reprogramming only after confirming the new/loaner module communicates correctly.
- Re-check: After any repair or replacement, clear codes, re-run full system scan, and perform a road or operational test to confirm fault does not return.
Likely causes
- Bad or unpowered FPCM (no battery feed or ground)
- Damaged connector or wiring at in-tank pump module or FPCM
- CAN bus open, shorted, or missing termination resistor
- Corrosion or water intrusion at service connector or harness
- Faulty scan tool interpretation or temporary network glitch
Fault status
Status
Lost Communication With Fuel Pump Control Module A — No valid CAN/LIN messages received from the fuel pump control module; DTC set when expected communication is missing or out-of-range.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
1
👎 Dislike
0
Send to email
Code
U0109
HYUNDAI
U — Network/User
Lost Communication With Fuel Pump Control Module
Views:
UK: 12
EN: 71
RU: 50
AI status
Completed
Completed
100%
Causes
- Fuel Pump Control Module (FPCM) failure
- Open, short, or high-resistance wiring between FPCM and network
- Corroded or loose connector at FPCM or harness
- Blown fuse or faulty fuel pump relay supplying FPCM
- Loss of module ground or supply voltage
- Faulty or missing CAN/LIN bus termination or bus short to battery/ground
Symptoms
- No start or extended crank (fuel pump not running)
- No prime when key is cycled
- Engine may stall or run intermittently
- Check Engine light / MIL illuminated
- Other modules report related U-codes or bus communication errors
- Fuel pump relay clicking or no audible pump operation
What to check
- Connect a professional scan tool and confirm U0109 and any related U-codes or freeze frame data
- Check battery voltage and health (should be ~12.4–14.5 V with key on/engine running)
- Inspect fuses and relays for FPCM and fuel pump circuit
- Visually inspect connectors and harness at FPCM, in-tank pump, and PCM for corrosion, damage, or loose pins
- Check for other modules that have lost communication (helps narrow bus or local fault)
- Perform wiggle/torque test on harness while monitoring communication and DTC status
Signal parameters
- Battery/ignition supply to FPCM: ~9–16 V (key on)
- Module ground continuity: low resistance, typically
- CAN bus idle (recessive) voltage: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (nominal)
- CAN dominant voltages: CAN_H ≈ 3.5–4.0 V, CAN_L ≈ 1.0–1.5 V during active bits
- Expected CAN bus differential voltage (dominant): ~2.0 V
- Termination resistance (two 120 Ω in parallel on bus) ≈ 60 Ω across CAN_H–CAN_L for a single network
Diagnostic algorithm
- Verify DTC: Connect a scan tool, record freeze frame and any additional U-codes. Attempt to communicate directly with the FPCM via tool.
- Check power/ground: With key ON, measure supply voltage at FPCM power pin and verify a good ground reference. Repair any open or low-voltage circuits.
- Inspect connectors/harness: Visually and physically inspect FPCM and in-tank pump connectors for corrosion, bent pins, or water intrusion. Repair or replace as needed.
- Check fuses/relays: Verify relevant fuses/relays for FPCM and fuel pump circuit are present and functioning. Replace faulty items.
- Verify network signals: Using a multimeter or oscilloscope, measure CAN_H and CAN_L at the FPCM connector with key ON. Confirm idle and dominant voltages and check for excessive noise or shorts to power/ground.
- Check continuity and resistance: With power removed, check continuity of CAN_H/CAN_L wiring back to the PCM and measure resistance across the bus for correct termination (~60 Ω).
- Isolate the circuit: If wiring is suspected, disconnect FPCM and inspect whether removing it clears bus errors or allows other modules to communicate. Trace/repair short or open circuits as found.
- Test under load/drive cycle: After repair, clear codes and cycle ignition; verify FPCM communication returns and that the fuel pump primes and operates normally.
- Module replacement: If wiring, power, and bus are verified good and communication still fails, consider replacing FPCM or performing module reprogramming only after confirming the new/loaner module communicates correctly.
- Re-check: After any repair or replacement, clear codes, re-run full system scan, and perform a road or operational test to confirm fault does not return.
Likely causes
- Bad or unpowered FPCM (no battery feed or ground)
- Damaged connector or wiring at in-tank pump module or FPCM
- CAN bus open, shorted, or missing termination resistor
- Corrosion or water intrusion at service connector or harness
- Faulty scan tool interpretation or temporary network glitch
Fault status
Status
Lost Communication With Fuel Pump Control Module A — No valid CAN/LIN messages received from the fuel pump control module; DTC set when expected communication is missing or out-of-range.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email