Powertrain, generic (extended)

P2A6B Alternative Fuel Rail Pressure Regulator Inlet Pressure Sensor Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2A6B is stored when the signal voltage of the regulator inlet pressure sensor drops below its valid band. With a typical three-wire transducer (5 V feed, signal, ground) that means a signal lead shorted to ground, a lost 5 V reference or a failed sensor element. A low voltage would read as an almost empty cylinder, so a bi-fuel vehicle may refuse gas mode or show an empty gauge with a full tank; Ford's 2003 bi-fuel CNG logic drove the gauge to empty whenever the sensor built into its regulator failed. GM uses the same reading on the Impala together with tank temperature to work out the fill level. No maker publishes P2A6B directly. Measure feed and signal at the plug with the key on before condemning the sensor.

Likely causes

Signal wire chafed through and shorted to ground
5 V reference open or pulled down by another sensor on the same feed
Inlet pressure transducer internally shorted

Symptoms

  • Check engine light on
  • Gas gauge shows empty although the tank is full
  • Gas mode refused, bi-fuel vehicle runs on petrol

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–600
Time0.5–2.5 h

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

Parts involved

alt fuel rail pressure regulatorwiring harnessafcm

Related codes

P2A69P2A6AP2A6CP2A6DP01A0

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