JCB P0628 – Engine ECU: Lift Pump Global Fault

The Engine ECU has detected a voltage in the fuel lift pump's control circuit that is below the manufacturer's specified range, indicating a general malfunction within the low-pressure fuel supply circuit. When this fault is active, the system typically enters a limp mode to protect the engine, reducing engine torque to 40-60% of its normal capacity, and may result in a crank-but-no-start condition.

• EcoMax Tier 4
• EcoMax Tier 4i
• EcoMax Tier 4 Final
• Loadall
• 444 Series
• 448 Series

1. 1

   Verify the fuel tank has sufficient fuel

2. 2

   Visually inspect the wiring harness and connectors between the ECU, fuel lift pump relay, and fuel lift pump for chafing, corrosion, or loose pins

3. 3

   Check machine earth points for secure and clean connections

4. 4

   Inspect connector terminals for debris or water intrusion, possibly from pressure washing

5. 5

   Check the fuel lift pump relay as a primary suspect

1. 1

   Read fault codes

   Use a diagnostic scanner like JCB ServiceMaster to confirm P0628 is the active fault. Note any accompanying codes, but address P0628 first as it can trigger others.

2. 2

   Repair harness and connectors

   Repair any loose connections or damaged wires found during the visual inspection. Clear the codes and re-test the system.

3. 3

   Test fuel lift pump relay

   Locate the fuel lift pump relay and check for a 12V supply to the relay coil. An open circuit on the supply or control (LSD) side can trigger the fault. Swap the relay with a known good one of the same type to see if the fault clears.

4. 4

   Test fuel lift pump circuit

   Disconnect the pump and check for voltage at the connector with the ignition on (pump may only energize briefly after key-on). Measure resistance of the power supply and ground circuits. For 12V systems: 0.8-1.5 Ohms, 4-8 Amps draw. For 24V systems: 4.9-5.7 Ohms, 4-5.5 Amps draw.

5. 5

   Check fuel flow

   If the pump appears to be operative electrically, check the fuel lift pump flow. Look for a restriction in a fuel pipe or a leak in the system.

6. 6

   Check Engine ECU

   If the wiring, relay, and pump all test correctly, suspect an internal fault within the Engine ECU's driver circuit. This is the least likely cause and should only be considered after exhausting other options.