What's a Output Speed Sensor?

[briwayjones]

I'm getting a P0171 code (System too lean Bank 1) and a P0720 code (Output speed sensor circuit). From what I've been reading there could be a lot of things causing the lean code but does the second code with it indicated something specific? Just from the descriptions to me it doesn't sound like they are releated but they always come up together. Does that second code give a clue as to why it's running lean?

 

[Turdle]

I wonder if the speed sensor and 02 sensor share the same harness---that is do they share the same wiring bundle? Pinout connector?

 

[Mbrooks420]

When I had the 0720 code I had a faulty OSS but it was obvious as it was shifting really randomly.

 

[dogfriend]

Is this code on the manual transmission truck in your sig?

P0720 is for an Auto Trans Output Shaft Speed Sensor.

 

[briwayjones]

Yes it is, it's on the truck with the manual transmission.

 

[dogfriend]

You shouldn't be getting that code (P0720).

Maybe you have a wiring issue, or something about the way the PCM is configured is giving that false code.

I would work on getting rid of the other code (P0171) first. I think that vacuum leaks are a common cause for P0171.

http://www.explorerforum.com/forums/showthread.php?t=145587&highlight=p0171

 

[briwayjones]

Ok, I poked around at the vacuum tubes. I didn't find any that seemed to be disconnected or cracked, that doesn't mean one isn't but I couldn't find one. I checked the bolts on the manifold just to make sure none where loose. Here's the conundrum. Should I take the chance that it's not a bad O2 sensor and that it's a more serious problem like a leaking manifold gasket and put it in the shop? Or should I spend the $60-$70 and change the Bank1 O2 sensor first and see if that's the problem before I put it in the shop?

 

[dogfriend]

Or should I spend the $60-$70 and change the Bank1 O2 sensor first and see if that's the problem before I put it in the shop?

You might be able to swap the O2 sensors from one side to the other to see if the problem follows the sensor.

I hate replacing parts without testing them to make sure they are actually bad, but that's just me and my cheap personality.

 

[NHale623]

Have you put a vacuum gauge on it?

 

[briwayjones]

Have you put a vacuum gauge on it?

No, how does that work? Where do you get one, price ect.?

 

[NHale623]

No, how does that work? Where do you get one, price ect.?

You should be able to purchase a vacuum gauge at any parts store for under $30.00.

Here are some links to a few pages that show the kind of information you can gather using a vacuum gauge.

http://www.secondchancegarage.com/public/186.cfm

http://www.centuryperformance.com/vacuum.asp

http://www.fordf150.net/howto/diagnoseengine.php

 

[briwayjones]

Thanks

 

[NHale623]

You're welcome.

It should help you to determine if the lean code is due to a vacuum leak, fuel delivery problem, or an internal engine problem.

Dogfriend had an excellent suggestion to swap upstream O2 sensors from one bank to the other and see if the code swaps with the sensors.

Good luck with your truck.

 

[briwayjones]

Hmm, I can't find any reference to a P0171 code as to whether it's refering to Sensor 1 or Sensor 2. Anyone know?

 

[dogfriend]

http://www.explorerforum.com/forums/showpost.php?p=1317392&postcount=3

 

[briwayjones]

Yeah I saw that thread. I might be blind but I don't see anything in there talking about sensor 1 or sensor 2 only bank 1 or bank 2. Bank 1 is passenger side, bank 2 is drivers side. But Sensor 1 is before the cat, and sensor 2 is after the cat.

 

[dogfriend]

I thought that you were asking if the code was for bank 1 or bank 2.

The sensors after the cat don't have any effect on fuel trim. They are there to check the efficiency of the cat(s). You will get a different code for the post cat sensor(s).

http://www.explorerforum.com/forums/showthread.php?t=154116&highlight=catalyst

 

[briwayjones]

Cool, that makes sense. Thanks again.

 

[briwayjones]

Well I went to see if I could fix the CEL one day. I ended up being too lazy to mess with the O2 sensors. So I pulled the MAF sensor. It didn't look dirty but I cleaned it anyway and cleared the CEL code. Well it's been about a week and a half since I've done that and no CEL again so far so I guess that was the problem.

 

[Lechuga]

I wonder if the speed sensor and 02 sensor share the same harness---that is do they share the same wiring bundle? Pinout connector?

Interesting thought