P2522: Air Conditioning Request B Circuit
What to do
Expect the air conditioning to work poorly or not at all, and possibly an idle dip or a stall at the moment it switches on. That stall is worth mentioning rather than dismissing — the module normally raises the idle speed just before engaging the compressor, and this circuit is how it knows how much to add. It is a signal fault rather than anything wrong with the compressor.
What this code means
A fault in the second air conditioning request circuit.
A second request line exists so the module knows not merely whether the compressor is wanted but roughly how much it will demand. Two lines give the climate system a way to signal a low or high level of cooling — a modest request on a mild day, a full one on a hot day with the system at maximum — and the difference in the load that follows is substantial.
Why the module wants to know in advance is the interesting part: it raises the idle speed before the compressor engages, not after. Waiting for the engine speed to drop and then correcting it would produce an audible dip and, on a small engine at a low idle, sometimes a stall. Knowing the size of the load that is coming lets the module add the throttle first and engage the clutch into an engine already carrying it.
That explains a symptom that otherwise looks unrelated: a fault in this circuit can produce an idle dip or a stall at the moment the air conditioning engages, because the module is being surprised by a load it would normally have prepared for. A car that stalls when the air conditioning is switched on at a junction is describing this rather than a compressor problem.
Likely causes
Start here
- Open circuit in the request wiring · moderate
- Corroded or loose connector · easy
- Faulty climate control panel or switch · moderate
Less common
- Faulty climate control module · specialist
- Damaged wiring harness · moderate
Symptoms
Components involved
Information, not instruction
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Community experience
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