U0424: Invalid Data Received From HVAC Control Module
What to do
Expect the climate control to misbehave — often no cooling at all, or temperature that will not settle.
Check that you can still demist the windscreen. If you cannot clear the screen, the car is not safe to drive in cold or wet weather, and that matters far more than cabin comfort.
Do not book a regas on the strength of this. A system short of refrigerant cools weakly and gets gradually worse. A system that has shut the compressor off because it does not trust a sensor cools not at all, and did so suddenly — and adding gas will not change it. The difference is worth describing accurately when you book it in.
Mention it if the engine idle has changed too — hunting, dipping, or stalling when the air conditioning is on. Air conditioning is the biggest load the engine carries, so a bad request from this module shows up as an engine problem, and that connection is easy to miss.
What this code means
The climate control module is broadcasting data that cannot be accepted as true. See U0400 for the family's framing.
Climate control looks like a comfort system and touches the engine more than people expect, which is why this code is not filed as low severity.
Air conditioning is the largest accessory load an engine carries. The climate module's request to engage the compressor causes the engine module to raise idle speed to meet it — so an implausible request can produce an idle that hunts, dips or stalls, and the driver experiences an engine problem rather than a climate one. The corpus makes the same connection at P2561.
The value most often at fault is a temperature, and there are several: cabin, ambient, evaporator, and the ducts. The evaporator temperature is the one with a consequence — it exists to stop the evaporator freezing, and a system that cannot trust it will disable the compressor entirely rather than risk icing it up. So no cooling at all, from a sensor rather than a refrigerant problem.
Before a regas is booked, that distinction is worth making. A system genuinely low on gas cools weakly and progressively. A system that has switched the compressor off because it does not trust a sensor cools not at all, and does so suddenly — and no amount of refrigerant changes it.
One practical check is available to the owner and costs nothing: the windscreen. Where the climate module has stopped working properly, the demister may not function — and a screen that cannot be cleared makes the vehicle unsafe in cold or wet weather regardless of how comfortable the cabin is.
The module's own faults are usually the connector or a blend actuator reporting a position it cannot have reached.
Likely causes
Start here
- Faulty climate control module · specialist
- Corroded or loose connector · easy
- Faulty receiving module input · specialist
Less common
- Damaged data bus wiring · moderate
- Faulty air conditioning refrigerant pressure sensor · moderate
Symptoms
Components involved
Information, not instruction
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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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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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