Powertrain, generic (extended)

P2523 A/C Request B Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P2523 reports that A/C request input B is pulled below its valid range. On the wire level this usually means a conductor grounded against body metal, a sending module whose output transistor has failed shorted, or a wet connector draining the signal. Whether the engine module then assumes a constant request or none depends on the circuit design, and no maker states it publicly; P2523 has no codegenau manufacturer documentation. The regulatory basis is CARB's A/C component monitoring, required only where the A/C changes fuel or spark control. Cars that receive the request over CAN, like the 2011 Saab 9-5, cannot set it. P2522 is the generic circuit fault on B, P2524 the high side, and P2520 the same low fault on input A. Expect missing or unwanted compressor operation.

Likely causes

Input B wire shorted to ground
Output stage of the sending module shorted
Moisture in a connector of the request line

Symptoms

  • Compressor not engaging or engaging unasked
  • A/C-related idle compensation missing

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€40–400
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

ac request input bhvac module

Related codes

P2522P2524P2520

References: law.cornell.edu, saabwisonline.com.