Fuel and air

P01A6 — Alternative Fuel Rail Pressure Sensor Circuit High

Severity: medium Drive with care, to a shop

What P01A6 means

The engine control module monitors the signal voltage from the alternative fuel rail pressure sensor and uses it to control the pump and valves. P01A6 sets when that signal stays above the expected range. It is usually an electrical problem such as a wiring fault or a bad sensor, but a real pressure control issue or a module fault is possible.

Symptoms

  • Check Engine light on
  • Rough idle
  • Loss of power
  • Reduced fuel economy
  • Hesitation or stalling
  • Long cranking or hard starting

Possible causes

  1. Faulty alternative fuel rail pressure sensor
  2. Damaged wiring or a poor connector contact
  3. Open in the sensor reference supply or ground circuit
  4. Faulty pressure regulator or volume control valve
  5. Worn or failing high-pressure fuel pump
  6. PCM fault (rare)

How to diagnose

  1. Scan for codes and freeze frame data, clear the code and see if it returns
  2. Inspect the sensor connector and harness for chafing, corrosion and loose terminals
  3. Compare specified and actual rail pressure during cranking, idle and under load
  4. Use a multimeter to check sensor reference voltage, ground and signal voltage
  5. Check low-pressure fuel supply: pump, filter and lines
  6. Test the regulator or volume control valve operation
  7. Where applicable, measure injector return flow
  8. If wiring and sensor are good, evaluate the PCM

Common fixes

  • Replace the fuel rail pressure sensor
  • Repair or replace damaged wiring and connectors
  • Replace the pressure regulator or control valve
  • Repair or replace the fuel pump or filter
  • Reprogram or replace the PCM once confirmed faulty

Questions and answers

What does P01A6 mean?

It means the alternative fuel rail pressure sensor circuit is reading too high. The cause is usually the sensor or its wiring, but actual pressure should be verified too.

Can I drive with code P01A6?

Only briefly and carefully until it is repaired. Power may be reduced and the engine could stall, so do not put off the repair.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.