U0466: Invalid Data Received From HVAC Control Module — Rear
What to do
The rear climate control is not working properly. The car is entirely safe to drive.
Before anything else, check the back of the car for water. Lift the rear carpets and feel underneath, look in the third-row footwells, check the boot floor, and look up at the headlining for staining if the rear unit is in the roof.
The reason is that the rear air conditioning makes condensation just like the front one, and that water has to drain out through a long pipe running through the vehicle. When that pipe blocks — and they do, with dust and debris — the water does not stop being made. It overflows inside the car. A damp carpet or a musty smell in the back is not a coincidence alongside this code; it is very often the cause of it, because the electronics are sitting in it.
Say so if you find any. Clearing the drain is the actual repair, and a module replaced without clearing it will be replaced again.
Two quick things to rule out first. On many cars the rear controls can be locked out by a switch at the front — check that. And if the front air conditioning is also not working, that is probably the real fault, since the rear system is usually switched off when the front one is unavailable.
What this code means
The rear climate control module is broadcasting data that cannot be accepted as true. See U0400 for the family's framing and U0424 for the front system.
A rear climate system on a large vehicle is not a set of vents fed from the front. It is a second system — its own evaporator, its own blower, usually its own heater matrix, its own temperature sensors and its own controls, fed by refrigerant and coolant lines that run the length of the vehicle.
Which brings the one thing this page exists to say, because it is the commonest real-world consequence and it is not obvious.
A rear evaporator makes condensate, and that water has to leave the vehicle. The front unit sits at the bulkhead and drains straight through the floor over a few centimetres. The rear unit sits under the floor at the back, in a side panel, or in the roof, and its drain runs a long way through the structure. Blocked with dust and debris, it does not stop making water — it overflows inside the vehicle.
So a rear climate code alongside a damp rear carpet, a wet third-row footwell, a musty smell or a stained headlining is one fault rather than two, and the module is usually the casualty rather than the cause. Finding the water is the diagnosis, and clearing the drain is the repair. Replacing a module without clearing the drain replaces it again later.
Two lesser notes. A rear system is normally disabled when the front is unavailable, so a rear fault alongside a front one is very likely downstream. And on many vehicles the rear controls can be locked out from the front — worth confirming before diagnosing a system somebody switched off deliberately.
Likely causes
Start here
- Water ingress into module · moderate
- Corroded or loose connector · easy
- Faulty climate control module · specialist
Less common
- Damaged wiring harness · moderate
- Damaged data bus wiring · moderate
- Faulty receiving module input · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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