U0624

Code

Generic U — Network/User

Lost Communication With Coolant Pump “B”

Brand: Generic

Type: U — Network/User

Views: UK: 23 EN: 47 RU: 32

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Page language: EN

Open or short in the communication bus (CAN/LIN) between pump module and controller
Faulty coolant pump module 'B' (internal controller failure)
Blown fuse or failed power/ground to the pump module
Corroded or damaged connector or wiring harness at the pump
Intermittent connection (moisture, bent pins) or poor ground
Network bus termination or wiring fault (low/high resistance)

Scan tool: read U0624 and any related codes, check freeze frame and occurrence count
Inspect pump connector(s) for corrosion, bent pins, moisture, or damage
Check fuses and relays supplying pump module power and control circuits
Verify good ground(s) at pump module and nearby chassis grounds
Check continuity and resistance on communication bus between pump and main controller
Use scan tool to monitor CAN/LIN bus traffic and attempt to command the pump

Expected periodic network messages from coolant pump module (manufacturer-specific CAN/LIN IDs and message intervals)
Typical idle CAN bus voltages: CAN_H ~2.5–3.5 V, CAN_L ~1.5–1.0 V (recessive) — verify with vehicle spec
Message frequency: pump status and heartbeat messages often in the 10–200 ms range (vehicle-specific)
Power supply: nominal battery voltage at pump connector with ignition on (~12 V) and during cranking
Ground: low resistance to chassis ground (

Connect a factory-level scan tool. Confirm U0624 is current or historical and note freeze-frame data.
Clear codes and reproduce the fault by cycling ignition/starting vehicle and exercising cooling system; re-check codes.
Visually inspect pump B connector and harness for damage, corrosion, or moisture; repair as needed.
Verify supply voltage and ground at the pump connector with a DMM. Replace blown fuses or faulty relays before continuing.
Monitor the network: use scan tool to watch for pump module presence/messages. If no messages, probe CAN/LIN lines for proper voltages and waveform with an oscilloscope.
Check continuity from the pump connector to the main gateway/ECU for communication lines; look for opens/shorts to battery or ground.
Attempt to command the pump from the scan tool while watching for response and bus activity.
If communication is intermittent, flex wiring harness while monitoring to locate break. Repair wiring or connectors.
If wiring, power and bus are confirmed good and the module still does not communicate, consider replacing or reprogramming the coolant pump module per manufacturer procedures.
After repair or module replacement, clear codes, perform any required relearn or vehicle configuration, and verify normal operation and no recurrence.