What are the common causes of P00C9?

A short to ground in the regulator A supply wire. Regulator A solenoid coil shorted internally. Water in the regulator A connector pulling the voltage down. Weak battery or low charging voltage on the regulator A feed. ECM driver fault holding regulator A low.

Check charging voltage and battery first. Disconnect regulator A and check the supply wire for a short to ground. Measure regulator A solenoid resistance against spec. Inspect the regulator A connector for water or corrosion. Command regulator A with a scan tool and watch supply voltage. Clear the code and retest.

P00C9

Fuel Pressure Regulator A Solenoid Supply Voltage Control Circuit Low

System: Fuel and air metering (P code)
Lamp: Check Engine Light
Category: Powertrain - Fuel/Air Metering

What it means

P00C9 means Fuel Pressure Regulator A Solenoid Supply Voltage Control Circuit Low.

Where it lives

For P00C9, the circuit described runs through the solenoid. The description of P00C9 reports a fault at the solenoid.

Check these first

A short to ground in the regulator A supply wire
Regulator A solenoid coil shorted internally
Water in the regulator A connector pulling the voltage down
Weak battery or low charging voltage on the regulator A feed
ECM driver fault holding regulator A low

What to do next

Check charging voltage and battery first
Disconnect regulator A and check the supply wire for a short to ground
Measure regulator A solenoid resistance against spec
Inspect the regulator A connector for water or corrosion
Command regulator A with a scan tool and watch supply voltage
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.