What does this mean?? The o2 sensor(s) is reading lean?? Any input on this situation??

2001 F150 4x4 5.4

There was also an evaporator system code, but I think maybe someone left the gas cap loose?

I unhooked the battery and it cleared everything. Truck started fine for a few tries. Will have it driven tomorrow to see if codes come back.

My reason for this is it was getting hard to start. I confirmed that fuel pump relay was not coming back on when cranking every time. Randomly it's fine, other times it won't start. Noticed it had CEL light, had it read at local Azone.

Don't know what to do about the "lean" issue?
What would tell the pump relay to NOT turn on?

I removed the cover from the relay and inspected points, they were fine. Check with ohm meter=good. Watched it function without the cap on it. Would prime everytime, but not come on when cranking every time.

 

Yeah, really common. Punch your fault codes into the SEARCH tool for many, many discussions.

 

disclaimer -- I'm no expert on these, but IMHO

pump won't come on a second time until the pcm gets a signal that the engine is 'running' -- not sure what that is, but somebody around here should know.

And maybe it's not getting that signal beacuse the truck isn't really firing that well ( fuel/ignition)

The O2 sensor lean reading means just that -- the engine is running lean, and no matter how much the pcm opens up the injectors, (within some kind of limits), the O2 sensor seeing excess oxygen - i.e. lean

Could be caused by
- fuel issues ( injectors/filter etc)
- vacuum leak ( I think only if it's a MAF)
- exhaust leak near the O2 sensor
- failing O2 sensor
- probably other things that I don't know about

Good Luck,

hj

 

Well the truck has 250K miles on it. Likely never had o2 sensors replaced(company owned since 16K miles). Always ran well, only couple coil packs have needed replaced since new, other then few other misc. wear items.

I watched the relay. It primes(I would turn key and wait for it prime before cranking), then soon as you crank, it turns on again to apply pressure as it starts. Did it a few times. Then randomly wouldn't cycle on and the truck would just cough/not start. Try again, then it would work and truck would start.

Seems worse when dead cold. Though won't start everytime when hot either. You would think the o2 sensors would not see/create issues when just started, only after running a moment(after they fully warm up).

 

Don't you think at 250k the truck just might begin to have issues?
You have to know what's behind the code discriptions for them to be of use.
To give you a start, the codes are in relation to the computer's software actions in response to sensor readings.
The lean codes tell you the software has shifted the fuel tables to the rich side out of limits, setting the codes. Hint, it's not the sensors.
What causes this?
Running to lean maybe or an air leak in the intake tract?
You can't work on these systems unless you have some idea of how things work.
Work on one issue at a time and do not try to guess and throw parts at it hopeing to get lucky.
List all the codes first, then what they tell you, then relate to the causes.
Look at the codes for being common to the same cause.
Often the common ones will all clear when the single cause is repaied.
What I am trying to do is get you to think about it in the right direction first off and look up some info because you have to do the work..

Good luck.

 

I'm thoroughly amazed it runs as well as it does. With a half dozen different people driving it all over the state(company truck).


As I posted earlier, the whole reason for this was a hard starting issue. Previously I replaced the fuel pump relay as it failed a few times. Mostly starting with hard starts, then no starts. Failed relay was the problem.

With a common issue again, that is where I started. The added CEL now also threw in a new "what" into the equation. I confirmed the relay was working properly, but was failing to come on randomly, thus the reason for the no start. A quick trip to Azone told me the three codes(lean 1 and 2, and evap system). I cleared everything by disconnecting the battery and the truck starts fine this morning. The gas cap is an aftermarket replacement, but in good shape so I'm thinking someone left it loose and thus the evap code.

I'll send it out today and see if the codes come back and then address them. I also mentioned I don't see the o2 sensors being the problem with starting, as they aren't in the loop yet. Though if they are failing, they could be sending a bad message to the computer and giving me the lean codes. Again, with the mileage I don't expect it to last forever and I just came here for some insight as I'm not a moron, but don't work on this newer stuff alot. I'm not going to just throw parts at it, yet. I want to duplicate to make sure it was not a fluke.

Thanks for the input.

 

The lean codes are usually either a dirty MAF or bad PCV hose elbow 97% of the time.

 

I had this code and Im ashamed to say the cause of it was.... *drum roll*....


the owner (me) Hadn't changed the air filter in 90k miles! Starved the engine of air. Just a thought, but check ur air filter to see how clean it is. It did set off lean codes for me

 

I'll say the filter is okay, only as we have oil changes done down at the monkey lube joint and they check it constantly.

Guess I need to poke around see if there is any bad hoses(PCV)?