Powertrain, generic (extended)

P2A6C Alternative Fuel Rail Pressure Regulator Inlet Pressure Sensor Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2A6C means the regulator inlet pressure signal sits above its plausible voltage ceiling. Typical causes are a signal wire touching a 5 V or battery-voltage circuit, an open sensor ground, an open signal line that the module pulls up internally (depending on its design), or an internal transducer fault. Unlike a genuinely excessive cylinder pressure, which P2A6F covers, the value here lies outside anything the sensor can physically deliver. On GM's Impala bi-fuel the regulator-mounted sensor covers a cylinder range of 3,600 psi; ITT's patented regulator places one transducer at the inlet port and a second at the outlet. No manufacturer documents P2A6C with thresholds. A broken ground often pins the reading at maximum, so check ground and connector first.

Likely causes

Sensor ground open or connector terminal pushed out
Signal wire shorted to 5 V reference or battery voltage
Inlet pressure transducer internally faulty

Symptoms

  • Check engine light on
  • Gas gauge stuck at full regardless of consumption
  • Gas mode blocked, bi-fuel vehicle switches to 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

P2A69P2A6AP2A6BP2A6DP2A6FP01A1

References: law.cornell.edu, static.nhtsa.gov, patents.google.com.