P0300 @ highway speeds
2003 silverado 2500HD 6.0L 4x2 ext cab - throwing a P0300 when driving above 40mph. Power is there. No unusual noises & such. Changed plugs & wires. Performed injector test @ local high school trades shop. Fixin to change fuel filter next. What else would cause code @ highway speeds? Thx.
The dreaded 300.. could be fuel or spark related. Check fuel pressure .. at least 58 psi and hold .
What kind of injector test? Check ..clean maf sensor . Best to check pressure go from there.
---------- Post added at 08:55 PM ---------- Previous post was at 08:53 PM ----------
Could be dist. gear .