My check engine ligt on my 99 Ranger 3.0L FFV has been on for a while, and it is pinging like crazy. I pulled into Autozone and they checked the code, and got error 1151. i thought it strange because don't they usually have a letter in front like P0 or something? Anyway, I did some trouble shooting before because I was having an EGR problem. The DPFE sensor is new, the voltage from th PCM to DPFE is ocrrect as well as voltage to the Vacuum selenoid. The vacuum selenoid resistence is correct, and I cleaned the Throtle Body. Also using double platinum spark plugs and changed the fuel filter. It is still pinging away and now I have this 1151 error. Any ideas?? Oh yeah, the EGR valve is good, it holds a 5-6 in-HG. Any help would be great i'm at a loss!

 

Hi, welcome to Ford Truck Enthusiasts!

The code is probably P1151 "Lack of HO2S-21 Switch, Sensor Indicates Lean... A HEGO sensor indicating lean at the end of a test is trying to correct for an overrich condition..."

HO2S-21 is the driver's side (Bank 2) Oxygen Sensor mounted before (upstream of) the catalytic convertor. Diagram here.

Your best bet is to look up that code here and read about the list of possible causes, and then go from there.