Technical Definition:

Fuel Pump Primary Circuit

Technical Description:

The fuel pump is activated by a PCM-controlled relay. Just as the name implies, a “relay” permits the transmittal of higher amperage current to the fuel pump without that current having to travel through the PCM (Powertrain Control Module).

Possible Causes:

• Short to ground on control circuit
• Fuel pump control circuit open
• Short to battery voltage on control circuit
• Harness chafing causing one of above conditions
• Bad relay
• Bad PCM

Possible Symptoms:

• MIL (malfunction indicator lamp) illumination
• No start condition
• No fuel pump operation
• Fuel pump runs all the time with ignition on

Fuel Pump Primary Circuit Malfunction

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Blown Fuel Pump fuse
– Open Fuel Pump Monitor Circuit
– Faulty Fuel Pump Relay
– Damaged ECM

Specific Makes: