1999 F-150. Service Engine Light troubles inside!
 

So we've owned our 99' F150 since 06' and it's never given us any grief and has exceeded our expectations with it's capabilities. However roughly about 2 and a half weeks ago the SEL came on. I took it to a local auto shop and had them scan the codes. The codes were P0171- System too lean, bank 1. Which I understand could be due to a vaccum leak, mass air flow sensor, or lean flowing injector. The second code is P1709- Park or Neutral position switch out of self-test range. The truck is a standard V6 5spd manual. Any advice would be greatly appriciated. Thank you in advance.

Cliff Notes:
-99 F150
-SEL, Codes P0171 & P1709
-V6 5spd manual

Alright I found the MAF sensor location and will be cleaning it tommorow. However I still have no clue as to where the Neutral saftey switch is located, anyone? TIA

The nuetral safety switch is a button or contact type switch that is pushed when you engage the clutch pedal to the floor allowing you to start your engine, without that conection or a bad connection you will run into not being able to start your truck. Just like sticking the key in the ignition and trying to start the truck without engaging the clutch pedal.

It is normally located at the top, front (closest to the firewall) of your clutch pedal.

Checked the MAF and it was clean as a whistle, so now it's on to the injectors I suppose. As for the safety switch I've never once not a single time NOT been able to start the truck or had any trouble. Thank you for the input.

just my 2 cents

if you have a lean code on just one side....and not both banks...focus on code bank side first (bank 1?)

one side code would usually rule out MAF and air cleaner...those would throw codes for both sides

make sure to check spark plugs on bank 1 side for damage, fouling or wear. replace if needed...how many miles since you changed plugs?

My 071 lean code was partially caused by worn out plug which didnt burn all the gas when running..dumping unburnt gas into the exhaust header on that side....the exhaust o2 sensor on the header reads the unburnt gas in the exhuast and in response reduces the amount of fuel going into the intake bank (all fuel injectors on that side) It will then throw a code when it gets out of acceptable range....

does it Idle smooth?

make sure you dont have vacuum leak in intake manifold on that side....spray carb cleaner around manifold on that side to check if engine sucks in carb cleaner and stumbles when idling

Dont spray hot exhaust parts tho....Poof!

good luck...

check this web site for information I found on your p1709 code............

http://www.automecanico.com/auto2001/fordobdll1000.html

good luck

One thing I always recommend with lean codes is to run a fuel injector cleaner of some sort in the tank. I prefer Sea Foam. It is a cheap way to rule out a dirty injector or injectors that could send the coade. Just my $0.02.

Well 2 bottles of injector cleaner later, and still the light comes back on almost exactly 3 days after resetting it via disconnecting the battery terminal. I took out the MAF sensor and it was clean as a whistle so I didn't even end up spraying any MAF cleaner on it.

I'll be swapping out the spark plugs tommorow and hopfully that will cure the problem, I've noticed the truck is running a tad bit rough/sluggish, more so when applying alot of load on the trans ie: up hills, or when getting on the throttle in a hurry. I appriciate all of the help and imput, you guys are lifesavers. Also the clutch functions perfect; wont start unless pressed in, never does it not start or anything else so I don't know why it's throwing that safety switch code.

One thing that is kind of odd, after I disconnected the battery, cleared the code, and got on the road about a day or so later I noticed the odometer sparatically go dim to where you can almost not read it. At first I thought the truck died but it was just the odometer lighting that was acting up, when I turned the truck off then back on it worked fine. It's done this about 3 times total in the last couple weeks and never before until I disconnected the batt... any ide-ers? TIA

check plugs and see what you get.....are they fouled or worn out?

did you check for leak?