Diesel Trouble Codes

P0087 — Fuel Rail/System Pressure Too Low (6.7 Cummins (EGR + DPF, pre-SCR))

Measured fuel rail pressure is below the PCM's commanded value on a 6.7L Cummins 2007.5–2012 (EGR+DPF, pre-SCR).

Updated September 2, 2026

What it means

The PCM commands a rail pressure but the rail sensor reports lower than expected, indicating insufficient high-pressure fuel delivery or control on this CP3 common-rail system with in-tank lift pump.1

Most likely causes

  1. Low-side supply restriction / failing in-tank lift pump — Insufficient volume/pressure to the CP3 inlet causes the high-pressure pump to under-fill the rail. Typical on this platform with in-tank supply pump.12
  2. Fuel control actuator (FCA / MPROP) performance or electrical fault — FCA regulates CP3 output; a sticking or electrically degraded actuator can limit rail pressure. Related circuit code family includes P0090.3
  3. High-pressure pump (CP3) wear / internal leakage — A worn CP3 cannot build commanded pressure; catastrophic CP3 failure has been reported to cause engine stoppage.4
  4. Rail pressure sensor signal error — Erroneous low reading from the rail pressure sensor can set P0087. Sensor circuit high is P0193 on this platform.5
  5. Rail pressure relief / pressure-limiting valve leaking — Mechanical relief valve on the rail can leak, preventing pressure buildup. Platform has a mechanical rail pressure relief/pressure-limiting valve.1

How to diagnose

  1. Verify freeze-frame conditions and repeat the fault under load.
  2. Monitor live rail pressure vs desired rail pressure with a scan tool; confirm actual low pressure.
  3. Check low-side supply pressure/volume at CP3 inlet; evaluate in-tank lift pump performance.
  4. Inspect fuel filter/water separator condition and replace if restricted.
  5. Check FCA command % and electrical values; compare rail pressure response to FCA changes.
  6. Inspect rail pressure sensor voltage and compare to a known-good reference; consider P0193 correlation.
  7. Perform a controlled leak test of the rail pressure relief/pressure-limiting valve and injector return flow to identify internal leakage.

Parts and tools you may need

Rough cost and difficulty

Parts and labor vary by region and vehicle condition.

When to see a pro

If rail pressure remains low after supply and filtration checks, or if metal debris is suspected from CP3 failure, have a diesel technician inspect the high-pressure system before further operation.

Sources

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

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

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

  4. NHTSA owner report 11366248 ↩︎

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

Watch a repair

Third-party videos, not ours — for illustration. Confirm anything against the factory service information for your truck.

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