What this test proves

Evaluate high-pressure control using scan data without opening the high-pressure system.

Tools

  • Scan tool with system-specific rail-pressure and command data
  • OEM pressure targets, units and fault-setting conditions

Preparation and precautions

  • High-pressure fuel can penetrate skin. Do not crack lines, touch suspected leaks or connect a low-pressure gauge to the rail.
  • Verify low-pressure supply first and follow the vehicle’s safe cranking/load conditions.

Connections

  • Connect through the diagnostic connector. Read the correct desired/actual pressure PIDs and relevant control commands.

Equipment settings

  • Use the same pressure units and reference for all channels. Select only necessary PIDs to preserve update rate.

Test sequence

  1. Record codes and freeze-frame before clearing.
  2. Log specified key-on, cranking, idle and permitted load conditions.
  3. Compare actual pressure rise, stability and response with desired pressure.
  4. Follow the OEM sequence for supply, sensor plausibility, regulation and leakage.

Expected signal / readings

Actual pressure should track the commanded behavior within the application’s limits. A sensor PID is a reported measurement, not independent proof of true pressure.

Interpreting results

  • Low actual pressure can involve supply, leakage, pump drive, regulation or biased sensing.
  • Agreement of PIDs does not rule out a shared sensing or data interpretation problem.

Common mistakes

  • Condemning the high-pressure pump from one PID
  • Mixing bar, kPa and MPa
  • Opening high-pressure lines to check delivery