P00C9

Code

Generic P — Powertrain

Fuel Pressure Regulator A Solenoid Supply Voltage Control Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 25 EN: 80 RU: 28

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Retrieve freeze frame and live data related to fuel pressure and duty cycle
Visually inspect wiring harness and connector at Fuel Pressure Regulator A for damage, corrosion, water intrusion, or poor pins
Check battery voltage and charging system (battery >12V, charging >13.5V with engine running)
Backprobe solenoid connector and measure supply/control voltage with key ON and engine running
Measure resistance of the solenoid coil with connector disconnected
Perform wiggle test on harness while monitoring voltage or codes

Battery/supply voltage at solenoid (key ON): ~12.0–14.5 V expected
Control signal (ECM output): typically a PWM or switched output that will vary between ~0 V and battery voltage when commanded (duty cycle 0–100%)
Considered low condition: control/supply measured consistently
Typical fuel regulator solenoid coil resistance (generic range): ~2–30 Ω — open = OL/infinite, short
If ECM grounds when energized, expect supply side ≈ battery and control side pulsed toward ground; if ECM sources, expect pulses toward battery — check vehicle-specific wiring

Read and record freeze frame and any related codes. Note engine conditions (temp, RPM, load) when code set.
Perform a visual inspection of harness and connector at Fuel Pressure Regulator A. Repair obvious damage and re-check.
Check battery voltage and charging system to eliminate low supply as cause.
With connector disconnected, measure solenoid coil resistance; compare to OEM spec. If open or shorted, replace solenoid.
Reconnect and backprobe connector. With key ON and engine off, measure supply/reference voltage at the solenoid supply pin — should be near battery voltage. Record reading.
Start engine or command solenoid via scan tool while monitoring control pin. Verify the ECM is commanding the solenoid (observed PWM or switching toward battery/ground). If the control voltage remains low (
If control output is present at ECM connector but low at solenoid connector, perform continuity and short-to-ground tests on the harness between ECM and solenoid. Repair any opens or shorts.
If wiring checks good and solenoid coil tests good, but control voltage still low at solenoid, suspect ECM output driver fault — verify with manufacturer procedures; replace ECM only after confirming harness/solenoid are good.
Clear codes and perform a test drive to confirm repair and that code does not return.

Wiring or connector fault between ECM and Fuel Pressure Regulator A solenoid (most common)
Corroded or loose connector at the solenoid
Failed solenoid coil (open or internally shorted)
Short to ground on the control/supply wire
ECM output driver failure (less common)