Diesel Trouble Codes

P0193 — Fuel Rail Pressure Sensor A Circuit High (6.7 Cummins (EGR + DPF, pre-SCR))

P0193 means the ECM sees the fuel rail pressure sensor voltage out of range high on a 6.7L Cummins 2007.5–2012 with CP3 common rail, in-tank lift pump, VGT…

Updated September 2, 2026

What it means

The ECM has detected that the fuel rail pressure sensor signal is higher than the expected range.1

Most likely causes

  1. Rail pressure sensor internal short / wiring short to voltage or chafed harness causing high signal — Sensor bias or signal wire shorted high; connector corrosion or harness chafe near the rail/valve cover can pull the signal high. Inspect sensor connector, wiring, and reference/ground circuits for damage or moisture.1
  2. ECM input fault / reference voltage issue — A fault in the 5 V reference or sensor ground can bias the rail pressure sensor high. Check reference voltage and ground integrity at the sensor connector and ECM harness.1
  3. Mechanical over-pressure event causing actual rail pressure to exceed sensor range — A stuck fuel control actuator (FCA/MPROP) or a stuck-closed rail pressure relief/pressure-limiting valve can cause real over-pressure. On this platform the high-pressure pump is CP3 with FCA/MPROP and a mechanical rail pressure relief/pressure-limiting valve on the rail.1
  4. Contaminated or failing rail pressure sensor — Sensor drift or internal failure can report high voltage even with normal rail pressure. Compare sensor voltage to a known-good baseline and compare actual rail pressure via scan tool to commanded pressure.1
  5. Low-pressure supply issue causing erratic pressure control — In-tank electric supply pump / fuel module is OEM on these years. Low supply can cause pressure control instability and sensor anomalies.1

How to diagnose

  1. Verify freeze frame and code history; confirm P0193 is present with engine running and at idle.
  2. Inspect rail pressure sensor connector and harness for chafe, oil intrusion, corrosion; check for short to voltage on signal wire.
  3. Measure sensor reference voltage and ground at the sensor connector; compare to spec and to other 5 V sensors.
  4. Monitor rail pressure sensor voltage and pressure PID vs. commanded rail pressure at idle and during a controlled ramp; look for voltage stuck high or pressure reading implausibly high.
  5. If sensor voltage is high with sensor disconnected, suspect wiring short to voltage or ECM fault; if voltage normal with sensor disconnected, suspect sensor internal failure.
  6. Check FCA/MPROP command % and actual vs. desired rail pressure to assess pressure control behavior; note that the platform uses CP3 with FCA/MPROP and a mechanical rail pressure relief/pressure-limiting valve on the rail.
  7. Inspect in-tank lift pump supply pressure and volume to rule out low-pressure supply contribution.

Parts and tools you may need

Rough cost and difficulty

Parts and labor vary by region and shop; diagnostic time is typically 1–2 h. Sensor replacement is modest; FCA/MPROP or wiring repair can increase cost. Always confirm with live data before replacing parts.

When to see a pro

If rail pressure reads implausibly high, if the FCA is commanding max/min with no change, or if wiring faults are suspected near the ECM, have a qualified diesel technician perform circuit tests and pressure verification. Do not attempt high-pressure fuel system disassembly. Stop diagnosis if safety-critical systems are involved. This is diagnostic guidance only. Sources:

Sources

  1. Curated DTC seed — 6.7 Cummins (EGR + DPF, pre-SCR) (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎