Powertrain, generic (extended)

P2561 A/C Control Module Requested MIL Illumination

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P2561 is a messenger code. The climate control module has found an emission-relevant fault in its own area, such as a component that feeds the engine's A/C idle strategy, and asks the engine module to switch on the warning lamp, since only the master controller may drive it. The engine module stores P2561 as a pointer; the actual fault code sits in the A/C module and must be read there. GM's 2012 hybrid table 12OBDG06 illustrates this split: the ECM is the master that controls the lamp, while other controllers store their own codes. CARB's section (e)(12) explains why A/C faults can be emission-relevant at all: wherever the A/C changes fuel or spark control, its electronic parts must be monitored. No maker documents P2561 publicly. Clearing it without fixing the A/C fault brings it back.

Likely causes

Emission-relevant fault stored in the climate control module
Failed A/C sensor or actuator behind that fault
Climate control module internal or software fault

Symptoms

  • Check engine light on
  • A/C may not cool or may be switched off
  • Further codes stored in the climate control module

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–600
Time0.5–2.5 h

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

Parts involved

hvac module

Related codes

P2519P2522P255FP256FP0645

References: law.cornell.edu, gsi.ext.gm.com.