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 October 15, 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

• Digital multimeter
• Scan tool with live data for rail pressure desired/actual and FCA duty
• Wiring diagram for rail pressure sensor circuit
• Dielectric grease
• Replacement rail pressure sensor
• Replacement FCA/MPROP if pressure control fault confirmed

Tools you’ll need

• digital multimeter — Measures reference voltage, ground, and signal voltage at the rail pressure sensor connector to detect shorts to voltage or an out-of-range sensor signal.
• OBD-II scan tool — Reads freeze frame and live rail pressure sensor voltage/pressure PIDs versus commanded rail pressure to confirm a stuck-high reading and assess pressure control behavior.
• fuel pressure gauge — Verifies actual low-pressure supply from the in-tank lift pump to rule out supply issues that can cause erratic rail pressure control.
• oscilloscope — Captures rail pressure sensor signal waveform to identify a constant high voltage or noise indicating a wiring short or sensor internal failure.

Rough cost and difficulty

Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying 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:

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources