It’s OK to admit when you are stumped working on check engine light issues on F250s. You might not have figured out that the faulty powertrain control module caused fuel pressure to increase, which caused the engine to flood and the code P0191 to set. Don’t be afraid to seek help, and read this Real Fix to diagnose the vehicle.

Vehicle

2006 Ford Pickup F250 Super Duty, 5.4L

Complaint

The customer states the check engine light is on.

Cause

Connected a scan tool and found code P0191 – Fuel Rail Pressure Sensor “A” Circuit Range/Performance. At idle, monitored the fuel rail pressure sensor parameter and found the measured parameter was out of specifications. Using a lab scope, measured the voltages present at the fuel rail pressure and found the reference voltage measured 2.3 volts when the specified voltage was approximately 5 volts. Disconnected the fuel rail pressure sensor connector, measured the reference voltage at the fuel rail pressure sensor connector, and found 2.3 volts was still measured. Disconnected the powertrain control module, connected test leads between the fuel rail pressure sensor reference voltage terminal and the reference voltage terminal at the powertrain control module, and measured the resistance of the circuit. The measured resistance of the circuit was within allowable specifications. Moved the test leads to the power and ground inputs for the powertrain control module, measured voltage and verified the powertrain control module was receiving all the necessary powers and grounds. This confirmed the powertrain control module had an internal defect and was faulty.

Correction

Replaced the powertrain control module, cleared codes, performed a road test and verified the vehicle operated properly. The check engine light did not illuminate and no fault codes returned.

Courtesy of Mitchell1 SureTrack Real Fix