Powertrain, generic (extended)

P2259 AIR System Control B Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2259 is the low-level fault of the second secondary air control circuit, B. A second circuit exists where an engine uses two AIR pumps, two relays or a separately switched air valve; circuit A keeps its own codes P2257/P2258. A low reading usually means the control wire has contact with ground. If the relay is switched to ground by the ECM, such a short can energise it permanently, so the pump or valve keeps running after the warm-up phase and may overheat. No manufacturer publishes a threshold for circuit B; GM merely names P2259 in the keyword list of its connector-check bulletin PIP5094 for 2014 and older models. For circuit A, GM's 2018 tables judge the low-side driver over 20 of 25 samples as a Type B fault. CARB requires that secondary air systems be monitored. The engine itself runs normally.

Likely causes

Control wire of circuit B chafed against the body or engine and shorted to ground
Relay or air valve B with a shorted winding
Corroded connector at relay B or the air valve

Symptoms

  • MIL on
  • Secondary air pump audible for longer than usual or while warm
  • Blown fuse of the secondary air pump after a long run

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–450
Time0.5–2.5 h

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

Parts involved

secondary air pumpsai relaysai wiring

Related codes

P2260P2257P2258P0411P0418

References: law.cornell.edu, gsi.ext.gm.com, static.nhtsa.gov.