Powertrain, generic (extended)

P2521 A/C Request A Circuit High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

With P2521 the engine module sees A/C request input A held above its valid range, typically because the wire touches a supply line, the input has lost its pull-down or the sending control unit drives it permanently high. Two makers list the code by number. Ford includes P2521 in the 2014 BOSS 302S engine module table without a lamp mark. FCA's emissions recall T21 for the 2004–2006 Dodge Sprinter names P2521 among the codes that the corrected engine software may newly report after reflashing. Neither publishes a voltage limit. CARB's A/C rules apply only where the request changes fuel or spark control. P2520 is the low counterpart, P2524 the same fault on input B. Drivers notice A/C that switches on by itself, will not switch off, or ignores the button.

Likely causes

Request wire shorted to a supply voltage
Climate control unit drives the line permanently high
Code newly reported after an engine software update (Sprinter T21)

Symptoms

  • A/C compressor runs although A/C is switched off
  • A/C button has no effect
  • Raised idle speed without A/C request

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 ahvac module

Related codes

P2519P2520P2524

References: performanceparts.ford.com, static.nhtsa.gov, law.cornell.edu.