Diesel Trouble Codes

P0090 — Fuel Pressure Regulator Control Circuit — 5.9 Cummins Common Rail

Fuel Pressure Regulator Control Circuit

Updated October 15, 2026

What it means

The ECM has detected an electrical fault in the circuit that controls the fuel pressure regulator on this platform. On the 5.9L Cummins Common Rail 2003-2007 ISB this is the Fuel Control Actuator (FCA/MPROP) control circuit on the Bosch CP3 pump. Code P0090 applies to this platform as FCA/MPROP control circuit fault.1

Most likely causes

  1. FCA/MPROP electrical fault or internal failure — The FCA/MPROP is the fuel pressure regulator on the CP3 pump inlet; an open/short or failed actuator can set P0090. Platform has Bosch CP3 pump feeding a common rail with a rail pressure sensor, a fuel control actuator (FCA / MPROP) on the pump inlet, and a mechanical fuel rail pressure relief / pressure-limiting valve on the rail. Rail-pressure codes P0087/P0088 and FCA codes P0090 apply here.2
  2. Wiring/connector damage to FCA control circuit — Chafed, corroded or loose wiring/connectors between ECM and FCA can cause circuit fault detection. Platform has Bosch CP3 pump feeding a common rail with a rail pressure sensor, a fuel control actuator (FCA / MPROP) on the pump inlet.2
  3. ECM driver fault for FCA control — Internal ECM output driver issue for the FCA control circuit can trigger P0090. Generic definition: The engine control module has detected an electrical fault in the circuit that controls the fuel pressure regulator.1

How to diagnose

  1. Verify code P0090 is present and check freeze frame for conditions.
  2. Inspect FCA/MPROP connector and wiring for corrosion, chafing, pin damage; check harness routing near hot/exhaust components. Platform has fuel control actuator (FCA / MPROP) on the pump inlet.
  3. Check FCA control circuit continuity and isolation to ground/power per service info; look for opens/shorts.
  4. Monitor rail pressure sensor data and commanded vs actual rail pressure with scan tool to confirm regulator control is affected; platform has rail pressure sensor with Bosch CP3 pump.
  5. If wiring and FCA check good, evaluate ECM output/driver for FCA circuit.

Parts and tools you may need

Tools you’ll need

Rough cost and difficulty

Likely repairPartsShop laborWho usually does it
Wiring or connector repair$10–$1001–4 hrsDIY with tools and a manual
Fuel pressure control valve (FCA/regulator)$100–$4000.5–2 hrsDIY with tools and a manual
ECM/PCM replacement (programmed)$600–$2,0001–3 hrsShop

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 diagnosis points to ECM driver failure or intermittent wiring faults that require harness repair or ECM evaluation, have a qualified diesel technician perform testing and repair. Do not attempt high-pressure fuel system disassembly. Platform has Bosch CP3 high-pressure pump feeding a common rail.

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

  1. Curated DTC seed — 5.9 Cummins Common Rail (curated) ↩︎ ↩︎

  2. Curated DTC seed — 5.9 Cummins Common Rail (curated) ↩︎ ↩︎

Repair videos: P0090 on the 5.9 Cummins CR

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

Diesel Talk | Bosch Fuel Control Actuator // MPROP — Diesel Power Products · 42K views