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P2522

A/C Request B Circuit

General electrical fault on the second A/C request input B. Many vehicles have two HVAC zones, a rear evaporator request, or a redundant request line — input B carries that signal. With the input invalid, the ECM cannot honour zone B compressor demand or rear-evap operation.

  • Check engine light: Yes
  • Emissions related: No
  • Repair difficulty: medium

Common causes

Ordered by how often each turns out to be the cause.

  • Open or shorted A/C request wire BCommon
  • HVAC module not transmitting request BPossible

Parts involved

  • AC Request Input B

P2522 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.