Heres my problem, and its driving me crazy. I've got an 01 f250 with the v10 4x4. The speedometer is not working and the o/d light is flashing, but i have no shifting issues. Pulled the codes and im getting a p0500 (VSS sensor A). Both sensors (one on rear diff, and one on the tranny have been replaced). I know these sensors can sometimes be bad from the get go but im at a lose. Any ideas? To be sure a bad instrument cluster would not cause the check engine light to come on, and the o/d light to flash? Any ideas? Also my clock spring is bad but dont think that would effect anything, could be wrong though. Thanks!!

 

Wire harness under the truck

 

Could u be more specific, BC have no idea where to start looking.

 

I would trace the wires from the rear diff to the cab. Could be anywhere in there. Look for open or frayed wires

 

Thanks will take a look first thing in morning

 

checked this morning and found no frayed wires or anything of the sort, any other ideas? Thanks for the help so far.

 

If you have a VSS code here are the only ways it can set, listed from most probably to least probable.

Bad sensor.
Bad connection between the PCM and the sensor. A bad wire may look just fine but not have electrical continuity.
Missing/damaged tone wheel in the differential.
Bad PCM.

One of those is your problem.

 

Thanks for the reply, ive been searching with no luck at all, found a post about ohms for sensors and tested all three even though VSS and the TSS are new. The VSS is reading around 1.8 and the TSS and the OSS are around 1.08 ohms. I have completely checked over the entire harness from cab to the rear end and no signs of warn/chafed wires. Any way to test at the plug of the VSS to make sure its receiving a signal? If the PCM was on the frits wouldn't it cause shifting problems... bc i have none, just the o/d flash and no speedo.

 

Have you electrically checked the wires, or visually checked the wires?

 

visual inspection checked out, but not sure how to test them with my fluke. Dont know range im looking for. So any input on how to test wires with a meter, i will go out and bare this 40 degree temps and 25 mph winds we have today. Want my truck working right again.

Bryan

 

Visually checking the wires is like checking the air pressure in your tires without a pressure gauge. You'll catch something obvious like a cut wire or a flat tire, but not most problems.

The best way to do this is to take it to a professional that knows how to diagnose wiring problems.

If you don't want to do that, get a meter. Get pins that mate to the female pins in the wiring harness so that you don't create problems by pushing a probe that doesn't fit into the female pins. The probe will expand the pins so that the connector won't make good contact when you put it back together. Then you'll have more problems than you do now.

Once you have the right tools remove the connector from the PCM and from the transmission. Using your wiring diagram so you know what you're looking at, check for continuity on each transmission wire to the PCM. Also check each wire for short to ground and short to power.

 

Mark, thanks for the great info! By any chance would you happen to know where i can obtain a copy of such wiring diagram? Just recently switched from a 02 chevy duramax to this new to me 00 v10 f250. So im not as familiar with the systems on these pickups like was on my duramax. Did all the work on my tuck myself, local dealer is untrustworthy. So with that being said I am competent in my mechanical abilities so with ur guidance hopefully i will get this annoying problem solved. Thanks again!

 

Also not sure if this might be of any importance...but since i have replaced and cleaned sensors, the speedo seems like it wants to work, like will read normal till about 10-15 mph then starts bouncing then goes to 0 an the o/d light will then start flashing.

 

An update, i have checked both wires from the sensor on rear end all way to the cab, and even inside the cab. I have checked for loose ground wires, and frayed wires all over the truck. Read in another thread about bad ground at the abs module at front of truck behind driver side head light, checked there all seems well. Well tonight for some reason i was riding down the high way and i noticed that when i activate the window switch or the lock switch or even hit the preset button on the radio the needle on the speedometer will jump. So im guessing there is an electrical problem somewhere. Anyone have dealings with something like this and know where else to look?

 

Sounds like you have an issue with poor ground connections. You need to clean and/or replace ground wires. Make sure all the grounds are good!