U0698

Code

Generic U — Network/User

Lost Communication with Coolant Pump “E”

Brand: Generic

Type: U — Network/User

Views: UK: 22 EN: 62 RU: 23

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Faulty coolant pump control module (internal failure)
Open, short or high resistance in CAN/LIN communication wiring
Power or ground missing at the coolant pump module (blown fuse, poor ground, relay)
Corroded/damaged connector at the coolant pump module or junctions
Bus termination problem (missing or incorrect resistor)
Software/configuration mismatch after module replacement or update

Symptoms

DTC U0698 stored in one or more control modules
Coolant pump may not operate or operate intermittently
Engine temperature warnings or engine overheating
Reduced engine performance or limp-home strategy (on some vehicles)
Other network communication DTCs present
Inability for scan tool to communicate with the coolant pump module

What to check

Connect a factory-level scan tool and verify U0698; view freeze frame and any related U or P codes
Check ability to communicate with the coolant pump module with the scan tool (module present on network?)
Inspect fuses, relays and power/ground at the coolant pump module connector
Visually inspect coolant pump module connector and wiring for corrosion, damage, pin backout or water intrusion
Measure battery voltage at the module with key on and engine off; check ground continuity to chassis
Check CAN/LIN bus voltages at the module connector (CANH, CANL idle voltages and differential)

Signal parameters

Module supply: nominal vehicle battery (~12 V) with ignition ON
Ground: chassis ground continuity required
CAN bus idle voltages (typical recessive): CANH ≈ 2.5 V, CANL ≈ 2.5 V; dominant state shifts CANH ≈ 3.5 V and CANL ≈ 1.5 V (differential ≈ 2 V)
Typical message update rate for status messages: commonly in the 1–20 Hz range (vehicle dependent)
Expected termination: ~60 Ω across CANH/CANL (two 120 Ω terminators in parallel)

Diagnostic algorithm

Record freeze frame and all DTCs from every module. Note whether other U-codes are present.
Attempt to communicate directly with the coolant pump module using a scan tool. If the module responds, view live data and status.
If module does not respond, inspect power and ground at the module connector (check fuses and relays). Repair as needed.
Visually inspect connector and wiring for damage, corrosion or water entry. Repair or replace connectors/wires if found.
With ignition ON, measure CANH and CANL at the module connector. Verify idle voltages and that messages are present with a scan tool or oscilloscope.
Check termination resistance across CANH/CANL with ignition OFF (~60 Ω expected). Repair missing/incorrect termination.

Likely causes

Blown fuse or poor power/ground to the coolant pump module
Faulty or disconnected wiring/connector on the CAN/LIN pair to the pump module
Failed coolant pump control module
Network termination/short on the CAN bus or bus wiring damage

Fault status

⚠️ Status

Lost communication with the Coolant Pump control module. The network is not receiving expected status messages from that module — check power, grounds, connectors, and CAN/LIN wiring.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours