What it means
Voltage on the fuel pressure regulator D control line is above the expected window. Wire shorted to B+ or coil open.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
Fuel pressure regulator D uses an electrically controlled solenoid to help regulate fuel pressure. The control module monitors voltage on its control circuit; P2C04 sets when circuit voltage is detected above the expected range, which can happen with a short to battery voltage or an open coil.
Common causes
Most likely first.
- Control wire shorted to B+
- Open regulator coil
- Connector pins corroded - high contact resistance
Symptoms
- Check engine light on
- Hard start, no start, or stalling under load
- Power loss especially at high load or rpm
- Possible long cranking time
How to diagnose it
- Use freeze-frame data and live fuel-pressure readings to establish when regulator D’s control-circuit fault occurred and how pressure responded.
- With the ignition off as specified by the manufacturer, inspect the regulator D harness for damaged insulation or contact with a B+ wire.
- Check the connector pins for corrosion, poor contact, or damage, and verify the circuit connections against the wiring diagram.
- Test the regulator D control wire for a short to B+ and check continuity with the circuit powered down according to the manufacturer’s procedure.
- If the wiring is sound, test regulator D’s coil for an open circuit and compare results with the manufacturer’s specification.
Common fixes
- Repair corroded or damaged regulator D connector terminals.
- Repair the control wire shorted to B+.
- Replace regulator D if its coil is open and wiring checks out.
Can I keep driving?
Avoid hard acceleration because regulator D may not control fuel pressure correctly; stop if the engine stalls or loses power in traffic. The fault can cause difficult starting or prevent the engine from restarting.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.