U0164: Lost Communication With HVAC Control Module
What to do
The heating and air conditioning will stop responding to the controls, and will usually sit at some fixed setting. The car drives normally.
The part worth planning around is demisting. It is the air conditioning that dries the air, not the heater — which is why the compressor runs on the screen setting even in freezing weather — so with the climate system stuck you may find the windscreen will not clear, or clears very slowly. In cold or damp weather allow extra time before setting off, keep a cloth in the car, and open a window slightly to help, because driving with a screen you cannot see properly through is genuinely dangerous rather than merely annoying.
Heated screens and mirrors may have gone too, since the same module usually runs them.
Otherwise this is not urgent mechanically, and as always the module itself is often innocent — its power, earth and the bus wiring come first.
What this code means
The climate control module has stopped being heard from. The general reasoning is at U0100.
The module normally falls back to a fixed default — a set temperature and fan speed, or nothing at all — and stops responding to the controls. On most vehicles the engine and gearbox are unaffected, which puts this among the milder codes in the family.
There is one consequence that is not a comfort matter and is worth taking seriously in winter: demisting.
A heater warms a windscreen; it does not dry the air. What removes moisture is the air conditioning compressor, which condenses water out of the air before it reaches the screen — and that is why the compressor runs on the screen setting even in freezing weather, on vehicles where the driver never asked for cooling. Lose control of the climate system and the screen may not clear, or may clear far more slowly, and a windscreen that cannot be demisted is a visibility problem rather than an inconvenience.
The same module usually operates heated front and rear screens and heated mirrors, so those may go with it.
Worth cross-referencing P2561: that code is the climate module asking the engine module to light the malfunction lamp on its behalf. If both are stored, the climate module was working well enough to make a request and has since gone quiet, which is a useful piece of sequencing.
Likely causes
Start here
- Corroded or loose connector · easy
- Failed power or earth supply to the module · moderate
- Damaged data bus wiring · moderate
- Blown fuse or failed supply · easy
Less common
- Water ingress into connector · moderate
- Faulty air conditioning control module · specialist
Symptoms
Components involved
Information, not instruction
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Community experience
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