Heres The Truck, 03 Gmc Reg Cab Shortbox. With The 4.8,. My Buddy Was Drivin It And His Light Ses Light Flashes On And Off, And Is Still Doing It, Heres The Codes, P0101 -maf. P0300-mulitiple Misfire,po332-knock Sensor. But He Said The Knock Sensor Codes Been On For A While . I Know What The Knock Sensor Codes Is But Not Sure On The Other Two. I Took The Maf Off And Checked It Out, No Trash In It And It Looks Very Clean.all The Connections Are There.ITS GOT 110K ON THE SPEEDO AND ITS RUNNING 45 FULL PRESSURE AT IDLE. Any Ideas?

 

Has he tuned it up at all? The SES light only flashes when the engine is missing hence the P0300. The MAF code could be from it getting wet , I have set 101 and 102 a bunch of times. As for the knock sensors...they probably need to be taken out and cleaned along with the connectors as they corrode when water gets in there and there's no place for it to go. The fix is to clean/install a new harness and silicone it. Also it could be a bad converter but I would think other codes would set.

Dave

 

Im Thinkin It Might Be The Fuel Filter, Its Looks Top Be Completely Stock And Has Never Beenchanged, And We Get Lincolns Like That Here All The Time(i Work For A Ford,lincoln,mercury Dealer).ifgthe Fuel Filter Is Stopped Up Where You Cant Even Blow Through It It Would Still Have Fuel Pressure But Would Idle. And It Idles Ok, But When You Press The Gas Slightly While Driving ,nothing Is There.i Put My Maf Of My Truck On There And Nothing Changed, So Im Not Sure About That Code.