The EGR system can cause several issues when something is wrong with it. Follow this Real Fix to see how a fouled EGR valve caused a code P1726 on this 2004 Ford F250 Super Duty with the 6.0L engine.
Vehicle
2004 Ford Pickup F250 Super Duty 6.0
Title
Check Engine Light Is On, P1726, Replaced Exhaust Gas Recirculation Valve
Complaint
The customer states the check engine light is on.
Cause
Connected a scan tool and found code P1726 – Insufficient Engine Speed Decrease During Self Test. With the engine at idle, monitored scan tool data and observed the exhaust gas recirculation valve parameter was erratic. Using the scan tool, commanded the exhaust gas recirculation valve to open and close and found the valve did not respond. Performed an inspection of the exhaust gas recirculation valve wiring harness and connector and detected no obvious faults. With the ignition on and the engine off, used a multi-meter to check for the presence of voltage and ground at the exhaust gas recirculation valve connector and found both were present. Removed the exhaust gas recirculation valve, visually inspected the valve and found that it was carbon fouled . The tests indicated the exhaust gas recirculation valve was faulty.
Correction
Replaced the exhaust gas recirculation valve, cleared codes, performed a road test and verified the vehicle operated properly. The check engine light did not illuminate and no fault codes returned.