Fuel and air

P0090 — Fuel Pressure Regulator 1 Control Circuit Fault

Severity: medium Drive with care, to a shop

What P0090 means

The engine control module commands the fuel pressure regulator electrically and watches how the system responds. P0090 sets when it sees an open, short or erratic signal in the regulator 1 control circuit. As a result, fuel pressure may not match the target and the engine runs poorly.

Symptoms

  • Check Engine Light on
  • Hard or long cranking
  • No-start
  • Hesitation or power loss under acceleration
  • Poor fuel economy
  • Black smoke from the exhaust
  • Engine stalling or cutting out

Possible causes

  1. Open or shorted wiring in the regulator control circuit
  2. Corroded or damaged connector at the regulator
  3. Failed fuel pressure regulator or its solenoid
  4. Faulty fuel rail pressure sensor
  5. ECM driver circuit failure or software issue
  6. Low-pressure fuel supply problem or contaminated fuel

How to diagnose

  1. Scan all codes and freeze frame data, noting any rail pressure sensor codes
  2. Inspect the wiring and connectors at the regulator and fuel rail for chafing, corrosion or heat damage
  3. Compare specified and actual rail pressure at cranking, idle and under load
  4. Check low-pressure fuel supply pressure and volume first
  5. Test power, ground and the control signal at the regulator connector with a meter or scope
  6. Measure regulator coil resistance and compare it to specification
  7. Check wiring continuity to the ECM and rule out shorts to ground or power
  8. If all is good, suspect the ECM driver and check for software updates

Common fixes

  • Repair or replace damaged wiring and connectors
  • Replace the fuel pressure regulator
  • Replace the rail pressure sensor if it is faulty
  • Reprogram or replace the ECM if it is confirmed bad
  • Correct low supply pressure and replace contaminated fuel

Questions and answers

What does P0090 mean?

It is a fault in the fuel pressure regulator 1 control circuit. The ECM sees an open, short or bad signal and cannot properly control fuel pressure.

Can I drive with P0090?

Only briefly and carefully. The engine may lose power or stall, so have it diagnosed as soon as you can.

What should I check first for P0090?

Start with the regulator wiring and connector, then compare actual fuel pressure to the target. A poor connection or damaged harness is a common cause.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.