JCB P0628 – ECM: Global Fuel Pump Malfunction - Short to Ground

The Engine Control Module (ECM) has detected a low voltage condition in the control circuit for the primary fuel pump (Fuel Pump A). This indicates a short to ground in the fuel pump circuit, which prevents the fuel pump from operating at full capacity or at all, leading to insufficient fuel delivery to the engine. This fault is primarily an electrical issue affecting the fuel pump's operation rather than a major mechanical failure.

• 3C
• 3CX
• 3D
• 3DX
• 4C
• 4CX
• 214
• 215
• 216
• 217
• 135
• 150
• 160
• 170
• 175
• 180
• 225
• 260
• 280
• 300
• 320T
• 330
• 520
• 526
• 528
• 530
• 535
• 540
• 550
• 560
• JS130
• JS140
• 8014
• 8016
• 8018
• 8020
• 8025
• 8030
• 8035
• 8040
• 8045

1. 1

   Record and clear the fault code to see if it returns immediately, indicating a persistent issue

2. 2

   Ensure the battery is fully charged and that all ground connections are clean, tight, and free from corrosion

3. 3

   Inspect all related fuses and relays to ensure they are functioning correctly (a buzzing relay can indicate a problem)

4. 4

   Visually inspect the fuel pump wiring harness and connectors for chafing, cuts, melting from hot components, or green corrosion deposits, and ensure all connectors are securely fastened

5. 5

   Use a multimeter to check the voltage at the fuel pump connector; a reading significantly lower than battery voltage (e.g., 6V) points to a circuit problem

1. 1

   Test wiring harness for shorts

   With the ignition off, disconnect the connectors at the ECM and the fuel pump. Use a multimeter to check for continuity along the power and ground wires. Measure resistance between the power wire and the machine's chassis; a low resistance reading confirms a short to ground.

2. 2

   Test fuel pump relay

   If accessible, swap the fuel pump relay with a known good relay of the same type to rule out a faulty relay.

3. 3

   Repair wiring and connectors

   Repair any damaged sections of the wiring harness or replace the harness entirely if damage is extensive. Clean or replace any corroded connectors.

4. 4

   Replace fuel pump and filter

   If the wiring and relay are confirmed good, the pump likely has an internal short. Relieve fuel system pressure, disconnect the fuel lines and electrical connector, unbolt the old pump, and install the new one. Replace the fuel filter at the same time to prevent contamination.

5. 5

   Final verification

   Clear the fault code and operate the machine to ensure the code does not reappear.