Below is autozone's link to the OSS in case you decide to get it. The orginal part numbers are within the autozone listing.

Duralast/Sensor - Transmission Speed (SU2345) | 2003 Ford Excursion 4WD 10 Cylinders S 6.8L EFI | AutoZone.com

 

Can anyone help. I have a 2002 F-350 7.3 Diesel. Truck doesnt shift properly when OD light is not flashing. When it flashes the shifting is good. Already replaced the Alternator and sensor in rear. Should iI replace the VSS or OSS sensor or look elsewhere.

 

The ONLY way to know what to do is to get the codes read. The places that read them free can't read the codes that are making the OD light flash.

If you want to do it without reading the codes, just start buying parts until it's fixed. Replace the VSS, OSS, TSS, TRS, all the solenoids, the wiring harness, the PCM, rebuild the trans. After all that is probably will be fixed.

 

Hi ,Mark Thanks for your reply . I had codes pulled ,they are 400 Fuel level sensor circuit faulty,603 Internal Control Module / Kam Error, 702 -gear 2-3 shift error and 733 Gear 3 Increase range. Does this make any sense. Dont know where to go next. I have a bad feeling and think i am going for a new trans. Thanks again for your help .John

 

The trans codes point towards a problem with the direct clutch. Usually that means a rebuild, but before spending that money on my say so, I'd get an opinion from a pro that can actually evaluate the trans.

 

Thanks Mark. Dropping it off at shop this week.

 

Mark (and others),
I am having similar problems and would appreciate some help. Its in my 2000 v10 6.8L Ford Motor. I am getting the:
P0720- output shaft speed sensor error

1st I replaced the sensor. I also replaced all the COPS (Did not have any misfires but moisture was in near the boots on about half of them).

After replacing sensor and Coils on Plugs, the same error was triggered again.

After paying close attention, it seems to only happen every once in a while when the engine is shifting from neutral the first gear. The OD light started blinking and triggers the check engine light and code. Usually the transmission seems very smooth otherwise.

Any idea what the next steps would be? Replacing the wiring harness? Do I need to get the transmission and torque converter checked?

Thanks,
Steve

 

Randomly changing parts is a very expensive way to try and fix this. Some diagnosis would be a good thing.

Start with electrically checking the wiring harness. This involves a meter. If no problem is found you'll need an oscilloscope for the next step.

With the oscilloscope look at the waveform in the alternator output. If an alternator diode has failed the output will have an AC component on top of the DC output. If this is getting a bit technical, it may be worthwhile to pay someone that has the right equipment and knowledge to do this for you. A very good independent shop would be my first choice. Some Ford dealers can do this, too. All of them should be able to, but only some can.

 

read post #9 and the issues i had.... now did you change the COP's AND boots, or JUST the COP's?

 

Had the same code and put in a new sensor Before I read this thread, doh!
Checked the COP'S and found the #2 Cop had a broken mounting hole and sand and other crap around the boot. I check the rest and they all seemed fine.

Houston, I think we found the problem. I replaced the COP and haven't had the code pop back up yet. It was a good excuse to finally get under the Ex and change the Transfer case fluid at least.

 

I already changed the COPS, springs, and boots. Two of them had moisture and grime near bottom of plug.

No misfire code though. After the COP fix, still spit out the error code.

I have not had a chance to try the harness diagnosis or the alternator check yet. I hope to soon and will report back (hopefully good news).

Thanks,
Steve

 

I seem to have joined you in the boat. I drove the Ex in the rain today and it spit out the Output Speed Sensor code again. I was lucky and had my scan tool with me so I pulled over and hooked it up so I could watch the streaming info. Everything looked fine while moving down the road. When I top at a red light the vehicle speed starts jumping around like an O2 sensor. The speeds start jumping all over when I'm not moving: 71,27,61,74,57,28, you get the idea.
I found 1 bad coil and the rest were fine, I added some dielectric grease at the plugs and boots connections to be sure they stay in good shape. I will be trying the alternator check tomorrow when it is not raining.
Any suggestions what to move along to checking if that doesn't find it?

 

Decided to take it to a shop instead of trying to do it myself, asked them to do the checks Mark recommended. Thought they did them (they didn't) then they told me that it was the VSS (which I thought was a different code and told them that). They told me it was fixed..... when I picked it up, code tripped before I left the parking lot.

Then when I asked if they electrically checked the harness, no visually checked. Did they check with a scope on the alternator, they don't have a scope to do that type of diagnostic but then was told that a bad diode doesn't cause the problem I asked them to check. They then told me they want to drop the pan to check the trans (but they outsource the trans work) and that they think the trans is bad. They didn't want to check the items. Never really dealt with this shop before but it was convenient and I thought I could get a quick answer.

I haven't had a chance to follow up on it again but I will be either do the checks myself or find a shop that can really do the diagnostic work. It would really upset me if I replace the trans and it was one of these other issues.

I realize this post isn't much help to anyone yet but I wanted to report back.

 

Here is a the AC Ripple Test that I used not only for checking things out, but also for learning: PDF download..... http://www.pvv.org/~syljua/merc/TooSeptST07.pdf

Here is another link with just the procedure: Alternating Current (AC) Ripple Test

 

Browser decided to double post. I only clicked it once this time.