What it means
Supply voltage to fuel pressure regulator A solenoid below expected range — fuse, relay or wiring fault.
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 A's solenoid depends on a supply-voltage feed to control fuel pressure. P00C9 sets when the control module sees that feed below its expected range, which can result from a weak supply, poor connection or wiring fault.
Common causes
Most likely first.
- Supply fuse blown or relay failed
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
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
- Record freeze-frame data and check regulator A supply voltage in scan-tool data, if available, alongside any related fuel-pressure codes.
- Inspect the regulator A connector and supply wire for corrosion, loose pins, chafing or heat damage.
- Check the relevant fuse and relay, and look for signs of a weak or interrupted feed.
- Measure voltage at the regulator A supply circuit under the conditions specified by the manufacturer and compare it with the manufacturer's specification.
- Check voltage drop and continuity across the supply path, then test the solenoid and control circuit using the manufacturer's procedure.
Common fixes
- Clean and secure a corroded or loose regulator A connector.
- Repair chafed or damaged wiring in the supply circuit.
- Replace a failed fuse or relay after checking for the underlying cause.
- Repair a poor ground or high-resistance connection confirmed by voltage-drop testing.
- Replace the regulator A solenoid only if testing confirms it is faulty.
Can I keep driving?
Avoid hard acceleration and driving where a stall would be hazardous; low supply voltage can disrupt fuel-pressure control and cause power loss or stalling. If it stalls or will not start reliably, stop driving until the circuit is repaired.
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.