03f15012

Well, the other day, the SES light illuminated in my dash. I was heading back to my dad's lot and luckily he has an OBD scanner. It pulled up this code P1151, which when i looked online was "Lack of HO2S-21 Switch, Sensor Indicates Lean" I reset it, and have not seen that light on again. This was probably about a week ago. Was this just a glitch in the system, or is the truck just slow to realize the problem again?

Carcrazygts2

Possibly a bad oxygen sensor. I'm currently going thru the same problem.

03f15012

I was thinking the same thing. It really came out of nowhere while i was sitting in the drive-thru at the bank. If it comes back on again, i'll look into it, see if thats my issue

udderbrudder

If you can read the datastream with the scan tool, check the values on the Long Term Fuel Trim. If it's more than 10% or so, you may have a vacuum leak .

03f15012

Thanks guys. If the light comes on again, i'll give this a shot, see what I find out.

vgavagan

Did you ever get the P1151 figured out? I've had that code on my '01 for a while now... just been living with it. I'm planning on trying to track it down this weekend. Pretty sure it's a vacuum leak in my case. The fact that I can actually hear a whistle is kind of a give away. At least, let's hope they are related!

The thing that seems odd to me is that I only get the P1151. I would think that a vacuum leak would cause a problem on BOTH banks. Why just the one?

03f15012

Not real sure about it. The light still has not come back on yet, so right now, im still saying it was a glitch of sorts.

udderbrudder

Depends on where the vacuum leak is. On an intake port at the intake manifold would make one cylinder lean and therefore the PCM will add fuel to every cylinder in the bank. Other things that commonly set this code are.....exhaust manifold leaks and cylinder misfires (which may not set a misfire code)

vgavagan

Thanks guys. So far I've only found one potential vacuum leak. The lower one of the two fat hoses going into the air intake right before the throttle body. The other end of that particular hose goes to the drivers side valve cover. I think it's just a crankcase ventilation tube. The short straight rubber part of that connection was old and loose. No way it could have been leak free. I don't know if that was THE problem, but it needed to be replaced so I replaced it. I also replaced a couple other little guys that looked dry rotted, but I don't think they were actually leaking.

I cleared out the codes, so far it hasn't come back. However, there are still a few tests that are incomplete. EGR and evap, I think. So I'll drive it around more tomorrow and see if I can get all to complete.

WORLDBOOK

P1151 code I went ahead and replaced both upstream O2 sensors bank 1 and 2 keep you posted if this fixes mine I'm running a 32 valve V-8 with Mach 1 and Cobra and Navagater parts along with some of the origanal F-150 parts as will I don't see or hear a vacum leak but will know in the next few days this truck is a parts nightmare so wish me luck WORLDBOOK