U02C1

Code

Generic U — Network/User

Lost Communication With Hybrid/EV Electronics Coolant Pump C

Brand: Generic

Type: U — Network/User

Views: UK: 16 EN: 30 RU: 14

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open, shorted or intermittent CAN high/low wiring between pump C module and vehicle network
Power (battery/ignition) supply or ground missing at pump C module
Corroded, bent or disconnected connector pins at pump C
Blown fuse or relay feeding the pump/control module
Internal failure of the pump C control module (electronics) or motor driver
Faulty vehicle gateway/module or bus termination problem

Symptoms

Hybrid/EV warning light and/or coolant system warning on instrument cluster
Reduced or disabled battery/pack coolant circulation for affected circuit
Related hybrid systems may derate or enter limp mode
No audible or electrical activity from pump C when commanded
Multiple communication-related DTCs on the same CAN bus

What to check

Read and record all current and history codes from all control modules; check freeze frame and data
Verify VIN-specific wiring diagram and locate pump C module and connectors
Visually inspect pump C connector and harness for corrosion, damage, or water intrusion
Check relevant fuses and relays for continuity and proper seating
Check module power and ground at the pump connector with ignition on
Scan for live CAN messages and attempt actuator bi-directional tests (command pump)

Signal parameters

Module supply voltage: battery or ignition supply present at pump connector (nominal vehicle battery voltage with ignition on)
Ground continuity: low-resistance path to chassis ground from pump module ground pin
CAN bus idle voltages: both CAN_H and CAN_L near the network common bias (approx. mid-rail when idle) and showing differential activity when bus is active
CAN message presence: expected periodic pump-status/heartbeat message IDs should appear on the bus (scan tool may list message interval in ms)
No or intermittent response when commanding the pump via diagnostic tool indicates lost communication

Diagnostic algorithm

Confirm code and check for related U-codes on other modules. Note whether code is current or past/intermittent.
Attempt to command Pump C with the factory scan tool or generic bi-directional tool and observe any response or current draw.
Inspect connectors and harness at Pump C for corrosion, water intrusion, broken wires or pin damage. Repair as needed.
Check and replace/check fuses and relays that supply pump power/IGN feed. Verify supply voltage at the pump with ignition on and during command.
Verify ground at the pump. Clean and tighten chassis ground points if high resistance is found.
With ignition on, measure CAN_H and CAN_L at the pump connector: confirm idle bias and active toggling. Compare to a known-good node on the same bus.
If CAN signals are absent or corrupted at the pump, isolate by disconnecting downstream nodes or using backprobing to find wiring fault. Repair wiring or connector faults.
If power, ground and CAN signals are present but the module does not respond, suspect internal module failure. Confirm with substitution or consult manufacturer service info before replacement.
After repair or module replacement, clear codes, perform relearn/initialization procedures if required, and verify proper operation during system test/road test.
If intermittent, perform extended driving/test cycles and monitor for recurrence; inspect for heat/motion-related faults.

Likely causes

Damaged connector or wiring harness at the pump (physical damage from routing or service)
Fuse or power relay for pump C circuit open or poor contact
CAN bus short to battery/ground at or near the pump harness
Pump C controller has failed and stopped transmitting on the bus
Loose or corroded ground connection at pump C module

Fault status

⚠️ Status

U02C1 — Lost Communication With Hybrid/EV Electronics Coolant Pump C. Stored when the vehicle control module fails to receive expected CAN messages from Pump C; may set hybrid/coolant system warning and disable circuit.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours