Continued Excursion troubles

[jsmall]

Due to previous problems (see Excursion power loss on hill in eng911 forum) I borrowed a car, so the excursion is parked for now (except for last night), so I guess this isnt a 911 issue, thats why I move this here.
I took the exc to my father in law's who has an Edge Evolution for his 94/96 ish PS to pull codes trying to find problem. On the way out the driveway, it starts acting up, I was stopped to put on seatbelt, engine starts hunting bad, lurching against the brakes. wierd.
Drive, OD off light now blinking. it goes out after 30 seconds or so. Then the exc. acts fine all the way to father in laws. Plug in the Edge, reads 3 codes:
P0722 No Signal from Output Shaft speed sensor
P0720 insufficient input from output shaft speed sensor
P0503 Vehicle speed sensor intermittant
I had tried to pull the codes with a centech code scanner from harbor freight, it only pulled the 720 code, I used it again and still only pulled the 720. Dont buy the centech scanner from HF.
Anyone seen these before?
I assume I need to replace the speed sensor.
Would the speed sensor being bad cause the problems I've been having?

[jsmall]

Is a way to test the VSS/OSS?

[jsmall]

VSS/OSS, one is on the transmission/transfer case, one is on the rear diff, right? Which one is which?
Why is there 2 sensors (aren't they basically the same, both reading driveshaft rpm)?

[jsmall]

I believe I found the answer:
The VSS is on the rear Diff, and it feeds the speedometer/odometer.
The OSS is on the Trans/Tcase and provides input to the brains of the truck.
I have seen them advertised as VSS/OSS, are they the exact same part (just 2 different locations)?
Please correct me if I'm wrong,
Thanks,

[jsmall]

Survey says:
VSS is on the rear diff, and does feed the instrument cluster.
OSS is on the Tcase (at the top, toward the back) but isn't installed on all vehicles. When installed, it feeds the computers.
They are the same part number sensor, just different locations and different purposes.
But knowing this doesn't fix my excursion.
Does anyone know if you can test one of these sensors? they are like $80 and I hate to buy one, just to check if its bad.
Thanks,

[jsmall]

Just replaced the OSS, seems to have cured the problem.

[Marty]

I know nobody responded to your thread but I want to thank you for working out your problem on the site. I'm going through the same problems right now and I'm working on getting it repaired.

I also did my own research and this some great additional information...

locate oss sensor (on Tcase near the back)
vss is on rear diff, runs speedometer/od.

The p0720 code means the OSS isn't communicating properly with the PCM. That's why I mentioned in a previous post what the OSS does, it may cause the of the OD light to blink.

Diesel tech
its the small sensor mounted on the top rear of tranny just in frt. of the tail shaft. theres also one on top frt.of tranny. it detects the rotational speed of the output shaft in correlation w/ the frt. input shaft. most likely it has something to do w/ the trannys internal componants though, not the sensor. could be the sensor though. hav'nt seen many go out. has the tranny been flushed or serviced?

Grampy Jim
Output shaft speed sensor... located at the rear of the trans case at the top... two wire connector.... All trucks have these... I'd check the wiring and the connector for damage before I replaced the sensor...

There is an identical connector attached to a sensor towards the front of the transmission... this is the Turbine Shaft Speed sensor...


P0720 is a OSS Sensor circuit Malfunction code. This is what it says in the shop manual:
Output Shaft Speed (OSS) Sensor

The output shaft speed (OSS) sensor is a magnetic pickup that provides transmission output shaft rotation speed information to the powertrain control module.

The output shaft speed (OSS) sensor is mounted externally on the top of the transmission case. The PCM uses the output shaft speed (OSS) sensor signal to help determine electronic pressure control (EPC) pressure, shift scheduling and torque converter clutch (TCC) operation.

What problems are you having right now?

Randy

Problem is the flashing OD light. I don't believe I have any drivability issues. Just want to make sure it doesn't leave me stranded somewhere. It seems to happen most often when I put it in 4WD to creep along the field etc..

Thanks!

Sometimes the OD light starts flashing because of a problem with the VSS sensor in the rear axle. This is where the speedo gets it's information from. Does you speedo ever malfunction from the 0 to 20 mph range?

Randy
I'd also check the wires running to the sensor.


Former diesel tech
P0720 - OSS "Output Speed Sensor" located in transmission tailshaft in autos only. That code, if set, will flash the TCIL, and may flash the MIL.

Buddy

[jsmall]

Glad to be able to help a little Maintain. I appreciate yours too.

[SUNTEC]

Hi to everyone out there I just joined here and wanted to say thanks and I also have a question.

for a week now my 2001 Excursion PS would crank and crank in the mornings and not start then I hook up the cables for a jump and it fires right up, I thought at first bad oil psi sensor and maybe just needed a little more umph to fire it up than usual, but today I get it started and the service eng light comes on and my overdrive light starts blinking and then I get a code P0720, so I google the code and it takes me to this thread. Would this sensor cause this.

Thanks for any help you can give.

Ed

[chappy]

Well I found this while searching.So what did you figure out cause mine is throwing the same code and shifting funny.Really light pressure when shifting and takes way to long to shift.Been doing it about a month now.I pulled 720 out of it along with 3-4 shift error a few times.