Code
U062B
Generic
U — Network/User
Lost Communication With A/C Refrigerant Distribution Valve Actuator “B”
AI status
Completed
Completed
100%
Causes
- Open or short in the wiring between the actuator and the network/controller
- Poor connector contact (corrosion, bent pins, damaged terminals)
- Blown fuse or missing power/ground to the actuator
- Failed/reduced CAN network (bus-off, missing termination, shorted CANH/CANL)
- Faulty A/C refrigerant distribution valve actuator “B” (internal electronics)
- Faulty control module (HVAC module/BCM) or software anomaly
Symptoms
- HVAC mode door or refrigerant distribution does not change or is stuck
- Reduced or incorrect A/C cooling performance in some modes
- DTC U062B present (may be stored with other network codes)
- HVAC controls intermittently non-responsive or delayed
- Possible diagnostic trouble codes for other modules due to network errors
What to check
- Scan for stored/active DTCs and note freeze frame/live data
- Attempt to actuate valve B using a scan tool and watch for response
- Inspect connector at the actuator for corrosion, water intrusion, bent pins
- Check fuses and power feed to the actuator circuit
- Measure supply voltage and ground at the actuator connector with ignition on
- Check CAN bus presence using a scan tool (module detected, messages present)
Signal parameters
- Communication protocol: CAN bus (module-to-actuator network)
- Expected supply voltage at actuator: ~12 V with ignition on (nominal battery voltage)
- Ground: low resistance to chassis ground (
- CAN bus idle voltages: CAN_H ≈ 2.5–3.5 V, CAN_L ≈ 1.5–2.5 V (recessive ~2.5 V each)
- CAN dominant state: CAN_H rises and CAN_L falls (differential voltage present during messaging)
- Message frequency: command/status messages typically periodic (approx. 1–10 Hz) — verify with scan tool
Diagnostic algorithm
- Retrieve all stored network and HVAC-related DTCs. Note any additional U0xxx/U01xx or U0073 codes.
- With a capable scan tool, attempt to command actuator B. Observe whether the module reports the actuator and whether any response is returned.
- Visually inspect the actuator connector and wiring harness for damage, corrosion, water intrusion, pin damage or poor retention. Repair as needed.
- Verify power and ground at the actuator connector with ignition on. If power/ground missing, trace and repair fuse, splice, or ground point.
- Check CAN network health: use a scan tool to confirm the HVAC/control module is present and publishing messages. Look for bus-off or missing nodes.
- Measure CANH and CANL voltages at the actuator connector while the network is active. Confirm idle and dominant voltages and proper termination resistance.
- Perform a wiggle test of the wiring from actuator to control module while commanding the actuator to detect intermittent opens/shorts.
- If wiring and network are good but actuator does not respond, bench-test or replace the actuator with a known-good unit and recheck communication.
- If actuator replacement does not restore communication, consider reprogramming or replacing the controlling module after verifying network integrity.
- Clear codes and perform a functional test of the HVAC system. Re-scan to confirm no reoccurrence.
Likely causes
- Connector corrosion or wiring damage to actuator
- Power or ground fault at actuator (fuse, splice or ground strap)
- Actuator internal failure
- CAN bus communication fault (open/short/termination problem)
Fault status
Status
Lost communication with A/C refrigerant distribution valve actuator "B" — actuator not responding to network requests.
Repair difficulty: Medium
Diagnostic time: 1.0 - 3.0 hours
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