I run the codes on my 98 ford f-150 with a 5.4 and got this.

1. P0171 - system to lean bank 1
2. p1131 - Lack of HO2s11 switches - sensor indicates lean
3. P1151 - Lack of HO2s21 Switches - sensor indicates lean
4. P0402 - Exhaust gas recirculation flow excessive detected
5. P0174 - System to lean bank 2


So its obviously running lean but how do i go about fixing it, i'mnot sure exactly what needs to be fixed to correct this problem.

 

Change the O2 sensors upstream of the cats.

 

The code P0402 is a seperate issue you have to address.
How long has this been going on?

 

Been goin on for a couple months now but i only drive the truck maybe once or twice a month so i havent exactly been in a big hurry to fix it.

I dont have any cats on it since it had true duals since i bought it but the pipes did end up breaking because the previous owner used cheap pipe and it rusted right behind the cab (extended cab). This happened about almost 2 months maybe 1.5 months prior to the check engine light.

Also i just have a cheap OBD II scanner i got from wally world the one that can pull codes and reset them, it was the $100 one if you know which one i am talking about.

If i put the full length exhaust back on is this problem gonna go away or is their more to it?

 

I would first fix the Egr valve problem sounds like the valve is stuck open or it has a bad solenoid or Evr. these are all things that are in the list to look at for the P0171 and the P0174 the other codes are for the O2 sensors not switching, if the system is maxed out it can't switch. Fix the EGR problem(P0402) and the other codes will go away.

 

Fix the EGR first, if you've got excessive EGR flow, it can dilute the air/fuel charge and make the upstream O2s read lean.

 

How can you tell wich 02 code is the upstream and downstream?Mine is reading a P1151 02 code as well, is that the upstream?

 

P1151 is bank 2 (driver's side) upstream.

 

If you have emmisions inspection you will have to replace the cat system as well as clear the EGR fault.
It's difficult to say what is causing what in the absolute but the EGR if stuck open could generate the OX sensor codes as well as air coming up the broken pipes in the absence of the cat system.
Another parameter is the down stream Ox sensors are a check the PCM uses to monitor the health of the cats. In their absence, the PCM knows there is a problem and can set codes from that alone as well as be influenced by the air that comes back up the pipes being broken or short.
Some people think they can get away with removing the cats for more power. It's doesn't work that way for normal street use.

I had ask how long this truck was running this way because I suspected that something else was going on for the codes you have listed.

 

Well it didnt show and engine light till alittle while after it got hit in the pass rear then it showed them. Could that be a possibility as to why?

Also is it worth buying a new EGR and seeing what that does? Or should i do something with the exhaust?

Also i dont have inspections or anything here in Iowa.

 

this might help
http://www.obd-codes.com/trouble_codes/index.php