U065B

Code

Generic U — Network/User

Lost Communication With Left Front Mode Actuator

Brand: Generic

Type: U — Network/User

Views: UK: 35 EN: 32 RU: 34

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open or shorted wiring between control module and left front mode actuator
Faulty or improperly seated connector at the actuator
Failed left front mode actuator (motor, gearbox, or internal electronics)
Blown fuse or lost ignition/switched power to actuator
Bad ground at actuator or control module
Intermittent or permanent network (CAN/LIN) fault

Symptoms

Loss of function for the left front mode (vent/flow/position) — actuator does not move or holds wrong position
Unresponsive HVAC/traction/door system functions that use the actuator (depending on vehicle)
Clicking or grinding noise from the left front corner when commanding mode
Multiple network communication-related DTCs present
Possible warning lamp or message on cluster related to system fault

What to check

Read and record U065B and any additional DTCs; capture freeze frame / vehicle state
Verify if actuator responds to manual or bi-directional commands from a scan tool
Inspect actuator connector for corrosion, bent pins, water ingress, or loose terminals
Check fuses and relays supplying the actuator circuit
Backprobe connector to measure supply voltage and ground with ignition on and while commanding actuator
Perform wiggle test on harness while commanding to reproduce fault

Signal parameters

Supply voltage to actuator: ~11–14 V with ignition on (no load)
Ground: near 0 V (low-impedance) at actuator ground terminal
Data bus: CAN_H/CAN_L idle ~2.5 V each (differential idle), or LIN bus idle pulled high to battery via pull-up — verify with scope
Actuator feedback signal: position potentiometer or PWM feedback (varies by design) — expected stable voltage or PWM when stationary and changing when commanded
Motor coil resistance: manufacturer-specific (typically low ohms); compare to service spec
Command frequency: if PWM-driven, typical frequencies can range from tens to a few hundred Hz — consult service data

Diagnostic algorithm

Confirm code and vehicle condition: document when code set, any freeze frame, and related DTCs.
Attempt to operate the left front mode actuator with a scan tool. Note response and diagnostic data (position, voltage, error status).
Inspect actuator connector and wiring for obvious damage, corrosion, or moisture. Repair any physical issues.
Check power and ground at the actuator connector while commanding actuators. Verify supply is present and ground is solid.
If power/ground are correct but no response, check the data bus signal at the actuator connector with a scope or lab-grade meter. Look for CAN or LIN messages and proper idle levels.
Wiggle the harness and connector while monitoring communication and actuator response to find intermittent faults.
If data bus signals are missing at the actuator but present at the module, trace the wiring between nodes for opens/shorts. Repair as needed.
If bus faults exist across multiple nodes, isolate by disconnecting suspected faulty nodes or segments and rechecking the bus.
If wiring and bus are good, bench-test or substitute a known-good left front mode actuator to confirm failure of the actuator.
After repair or replacement, clear codes and perform functional test and road/operational test to confirm the fault does not return. Re-scan for related codes.

Likely causes

Connector pin corrosion or loose terminal at the actuator
Damaged wiring harness (chafing, broken wires) to the left front actuator
Failed actuator motor or internal controller
Local ground or power supply fault
Network messaging fault caused by another node pulling the bus down

Fault status

⚠️ Status

Control module has not received expected communication/feedback from the left front mode actuator. The actuator is not reporting position or responding to commands; fault may be due to wiring, power/ground, data-bus, or actuator failure.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

Repair manuals