U0659Lost Communication With Left Front Temperature Actuator
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- In a two-zone system the left front temperature actuator turns the blend door that sets how much of the air for the left side passes the heater core. As a smart LIN node it takes position requests from the climate master and replies with its state. GM documents U0659 in the body control module of its 2025 OBD tables (25OBDG03B, 25OBDG04B): the actuator reply frame missing for at least 11.5 s, evaluated every 600 ms with the battery above 11 V and no sooner than 5 s after power-up, Type B, so the MIL comes on after two trips. While it is active GM holds back the door checks B2B05, B2B28 and B2B29; corrupt counters from the same motor are GM's own U140F. The left zone, on US cars the driver, then stays at one temperature. U065A is the right-hand twin.
- What you may notice
- Left zone stuck hot or cold regardless of the setting
- Check engine light on GM vehicles that list the code as Type B
- Climate display may show a fault or ignore left temperature changes
- Likely causes
- LikelyElectronics of the left temperature actuator failed
- PossibleLIN, supply or ground wire to the actuator open or chafed under the dash
- PossibleActuator plug not latched after dash or footwell work
- RareConfiguration or software fault in the module that polls the actuator
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €40 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.