1999 Ford F-450 7.3L Diesel Spits and Sputters with P0198 and P0476 Codes - Diagnosis and Fixes
Hello everyone, I'm having a serious issue with my 1999 Ford F-450 2WD 5-speed dually with the 7.3L diesel engine. The truck is spitting and sputtering severely, acting like it has water in the fuel system. When driving, the P0198 code (Engine Oil Temperature Sensor Circuit) appears and causes the engine to run rough, surge, and sputter. Recently, during a KOER test, I also received a P0476 code, which according to the definition is related to Exhaust Pressure Control Valve Range/Performance. All injectors have been replaced, injector harnesses at each injector have been replaced, and valve covers have been checked—no shorts detected. I've done extensive testing with no signs of electrical or mechanical faults. Has anyone else experienced this combination of symptoms and codes? Any insights on how to diagnose or fix P0198 and P0476 in a 1999 F-450 7.3L diesel?
P0476 indicates a problem with the Exhaust Pressure Control Valve (EPCV) — specifically, its range or performance. Replacing this valve is likely necessary and may resolve both the P0476 code and improve symptoms related to the P0198 code. I recommend checking the EPCV first, especially since it's a known issue in 1999-2003 Ford 7.3L diesel trucks. Once replaced, monitor for improvement in engine performance and fuel delivery. Good luck — please update with your results.