Powertrain, generic (extended)

P2A6D Alternative Fuel Rail Pressure Regulator Inlet Pressure Sensor Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2A6D is the dropout code of the regulator inlet pressure sensor: the signal jumps or briefly vanishes, but not long enough for a steady low or high verdict. The regulator normally lives in the engine bay, next to the right-hand strut mount on GM's 2015 Impala bi-fuel, and Blackstone requires warm engine coolant to circulate through its SAN209 unit so that it does not ice up. Its connector therefore sees heat, vibration and condensation. Loose terminals, a harness chafed against coolant hoses or moisture inside the plug are the usual suspects. No manufacturer publishes P2A6D; CARB expects circuit faults of such inputs to be detected. Wiggle-test the harness while watching live data, and look for corrosion in the connector.

Likely causes

Loose or widened terminal in the sensor connector
Condensation or corrosion in the plug near the coolant-heated regulator
Harness rubbing on hoses or brackets with intermittent contact

Symptoms

  • Check engine light on, sometimes clearing again
  • Gas gauge flickers or jumps
  • Sporadic switch from gas to petrol while driving

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–500
Time0.5–3 h

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

Parts involved

alt fuel rail pressure regulatorwiring harnessafcm

Related codes

P2A69P2A6AP2A6BP2A6CP01A2

References: law.cornell.edu, static.nhtsa.gov, blackstonecng.com.