I thought I'd post this up on the chance it might help someone else at a later time...

So my OD light started flashing recently so I used AE to pull the codes and it said P0500-Vehicle Speed Sensor malfunction. The odd thing is that the speedometer was reading correctly and when I switched over to monitor the ABS system the rear speed signal was present.

I 'assumed' the PCM was calculating vehicle speed via some other method such as the front wheel sensors or maybe even the OSS sensor in the trans and was simply feeding that info to the ABS and dash cluster. Assuming things gets me into trouble more times than not because I was dead wrong in this case (but I'll get to that in a moment...).

So, I picked up a spare sensor for $30 and proceeded to change it out. When I crawled under the truck I found damaged wires at the VSS. Looks like the previous owner got happy with a cutting torch and burned the insulation off the wires. So, I fix the wires and did not change out the sensor since I figured it was the wires that caused the fault. I test drive and it worked for a mile or two but then the OD light began flashing again.

So, back under to change the sensor. Test drive and OD light STILL flashing.

Out comes AE again and I road test. In Enhanced Systems, I monitor Vehicle Speed and it sits at dead zero. Switch over to ABS Systems and rear speed sensor shows correctly. I pull over, unplug the connector at the VSS and check again and to my surprise ABS light comes on and rear speed value is zero. Hmmmm....???

So, obviously my assumption earlier was incorrect. I pull out the wiring diagrams and see that the VSS actually feeds the ABS module directly and then it branches off into 7 possible circuits such as the GEM, Overhead Console, PCM, instrument cluster and a few other places. So, ABS has speed, overhead console has speed, instrument has speed.....only item that doesn't have speed is the PCM (hence the P0500 code). The wire color from the ABS to the PCM that provides the speed is grey with black tracer. I might have a break in that wire.

This is when I learn my lesson to beware of modified vehicles. This particular truck has a Banks Brake installed. Step 36 of the installation instructions say to locate the Grey wire with black stripe and install a T-Tap splice for the Computerized Brake Controller module. Turns out that connection is faulty because I gave a tug on the wire and it pulled right out of the T-Tap. Wonderful. At this point I am giving up for the night but I am pretty confident that I found the problem.

Without AE and the wiring diagrams I probably would have never found the faulty splice connection because I would have been looking elsewhere the entire time. I am so glad I have this software and kick myself in the behind for not getting it sooner than I did. Hopefully others can learn from my mistakes.

Cheers.

 

Wow, so I guess we were not too far off on the way the speedo works when we talked the other day.
I never would have figured a broken wire. I hate t-taps.

My Cummins has them on the chip, the fuel solinoid enrichment on the pump is hooked up with scotch lock connectors. I have had nothing but problems with them.

I need to just pony up the dough to get my own AE.... maybe when taxes are back....

 

Scotchlok = Bad
Filled Scotchlok = Reliable
I've used thousand of these in my career and vehicles/trailers without any issues after a proper crimp. [LINK] They have different styles and sizes, but filled is the only way to go.

 

It is amazing what good troubleshooting and the proper documents can help you do!

 

Good troubleshooting! Reps sent.

 

Yep. I think you had it figured correctly and then you started talking to me and I confused the issue.... I am not entirely certain yet...but it appears the system works one way for '99-'01 models and then might be slightly different for '02-'03 years. I was looking at the '02 wiring diagram this morning (thanks Ken ) and I see that it is different from the '99 version in regards to wire color for that signal. The PC/ED manual for model year 2003 states the instrument cluster is on the SCP bus so maybe that is the difference. I'll have to look into that a little bit more...

I've never liked the T-Tap product either. Unfortunately they seem to be standard equipment with Banks products so the previous owner has those things all over this truck. It will take me a while to eradicate them all.

Agreed. We have had good luck with the filled Butt and Dropwire connectors once 3M came to our facility and showed us how to set them properly. Prior to that we were having all sorts of issues with those things. The Butt connectors are fairly straight forward but the Dropwire connectors really should be used with their special tool...or a pair of linesman pliers at least.

For a while our technicians were cutting those things out and using wire nuts to make up the connections but that was actually making things worse for us. 12V & 24V DC systems do not like the extra resistance that wire nuts create so the Scotchlok products are helpful when used properly. The design of the T-tap is kinda poor IMO....I am glad that product isn't in the 3M catalog any longer.

You can say that again. Without the info from AE and the wiring manual I would have been swimming upstream the entire time on this issue.

Thanks for the reps!

 

First I'd like say, I understand this thread is old, I'm only posting here because this is the fist thread that populates with a Google search of "Ford F250 P0500 code". After what seemed like 1000's of forum threads and countless hours of tracing wires and replacing sensors, I finally fixed my ABS light/no speedometer/DTC P0500. I would just like to give feedback on this issue just in case it can help someone else experiencing the same symptoms.

My ABS light/speedometer was an intermittent problem, working when it wanted and not working the other half. After replacing the VSS/ABS sensor on the rear differential, replacing the pigtail connector, and testing the wires between the sensor and the ABS module for weeks I had almost given up. I found a thread on another forum breaking down what to check for each given code (will repost a link after this post). I had check my fuse multiple times, along with the ABS module ground found near the radiator mount. Well today I decided to give it another shot.

My ABS fuse (mini fuse 11 with the fuse box in the engine bay) was not making a good connection within the fuse block. After checking this fuse multiple times and even replacing it with brand new 10amp fuses, I never paid attention to how well it seated within the fuse block. I slightly bent the fuse prongs in opposite directions creating a much better connection. Immediate results after starting my truck. Code is gone, no ABS light, and my speedometer works as advertised. I'll finally sleep better tonight knowing that I won't see an ABS in the morning when I get in my truck!

I know this isn't the "fix all" if other members are having these same symptoms, but definitely something to look into. I spent hours troubleshooting something so easy to overlook.

I'll close this post, my first post to this forum (not new to forums by any means, just this one), with a big thank you to all the knowledge that resides here, many hours have been spent reading through the posts within this site that have been very educational.

 

ABS Light - Ford Powerstroke Diesel Forum

This breaks the DTC codes down, I had read this so many times, and checked both areas for "P0500" multiple times as stated above. It wasn't utility I slowed down and noticed the loose fuse in the fuse block u til I resolved my issues.

 

Thanks for reporting that! As these trucks age, more and more obscure stuff will occur, and sharing this will certainly help somebody sooner or later.

 

I read this and found it a good read and full of important ABS code stuff, when looking a bit closer began to ask myself if this applies to 99-03 /7.3 diesel or is this on a 6.0 PSD? If so, are codes the same, wiring the same?

As for me I'm a newbie and need to learn much more. Also what is a AE and where to purchase that and wiring diagrams. That would also help greatly.

 

Great Job tracking down the problem. This was very helpful and insightful when I was trying to figure my P0500 & OD light blinking. I had this issues 6 different times and so far 4 different reasons I ended up with a P0500 & OD blinking.
Mind you I don't have AE so I only have been able to figure out problems with the help of the FTE brotherhood for sharing their knowledge with me.
Thanks Greg !!

 

"VSS signal Splits 7ways" were too
Helping a fellow diesel enthusiast that was at the diesel getten spot looking for advice.
he changed the doors and bed then discovered no spedo...

pcm shows speed correct no codes

gpm shows 0mph no codes was replaced by ford

overhead console shows p0500

speedo shows 0 , no sweep at key on factory and 2nd cluster (ford sent the broke truck back after 3months saying new/diffren cluster. Nope)
what is the signal to the actual gage motor can I hit it with a 5vdc or 12vcd , PWM or a pulsed(on off at a high enough frequency drive the needel to confirm functionality and not a burned winding x2 speedeos

trans shifts perfect

no abs light

no O/D light

gry/bl showed continuity from pin 7 to GPM pin 25(? 1 left and 1 up from bolt hole on the brown/ inbord plug ) =0.3ohms 0.0vdc

No more throw a VSS at it there cheep($18 paid 2021). Test your VSS with your drill.
new VSS new and old VSS will show speed at pcm when held to the side of a drill near the motor(motor magnets/ back emf trigger the VSS causing the pcm to respond with a drill opperator variable speed reading.

i checked cluster c250d pin 7 vehicle speed signal and 13 speed control indicator ground input ,for an AC , DC , Hertz , continuity from each other and ground ~420-450mvdc from pin 7 to 13

it was said to check the harnness "electrically" for smoshed chafed/nicked wire. . Do you mean ohm test the VSS circuit ?
Ill be meating up with some one in the morning to try and figure this out some more

 

Gumby, I'm going to bump this so someone who is more in the know might lend a helping hand. This thread is 9 years old, so I doubt many of the posters in the original thread are still active. I was around back then but most of them aren't.

 

Not certain of the three possibilities
Corroded ground rear of the 2 next to the batery

3wire dead end pig tail was un pluged from its cap(possibly a jumper) tgat is bolted to th finder next to the questionable ground.

gpm plugs were not properly seated...

makes me think the customer had a problem before the body shop started working on it and just got pined with problem

 

I have been chasing this problem for so long in my E Superduty 1996.5 Cutaway Shuttle bus and finally think I have solved it! I was getting P0500 VSS code, the OD light would blink, and would go into limp mode, hard shifts. At first I thought the VSS (RABS) sensor since that's where my code lead me. Bought a new VSS, (plastic) learned that its not calibrated right so will cause a similar issue any time I exceed 55. Changed the gasket on the original VSS and reinstalled it. Replaced VSS pigtail. No Help, the whole time I owned this bus it had intermittent hard shifts, I know I was damaging the transmission and it was a computer issue, not a fluid or something mechanical. I finally realized this is because the brake light circuit was controlling the transmission, and the PCM thought I was using the brakes because of an intermittently shorting connection in the brake circuit. This brought me not much closer to finding it. It did make it easy to raise my fist to the sky and curse whatever engineer thought it was a good idea to make a transmission rely on the brake light circuit. Why not use the pedal? In my case the culprit was a broken piece of aluminum which was supposed to connect the cases of my passenger side taillight assembly. This was causing the top most bulb to lack a ground, although it was still illuminated. All of my symptoms of lights not being illuminated at the proper time were happening on the drivers side, so I was mostly inspecting the drivers side connections over and over again. Finally, I checked out the passenger side and found this! Its not a wire at all! Just a corroded piece of aluminum that is no longer attached to serve as a grounding point. I added a wire, screwed in at both ends to this aluminum casing and the one beside it, to complete the ground circuit path. The illuminated filaments on the bulb with the case with a poor ground (top) suddenly reversed which filament illuminates when. All tail lights and side lights are functioning as they should, and I am confident that my brake light grounding issue is now cleared up, since I have gone through this vehicles wiring so many times. I haven't even gone for a test drive yet and already I am looking forward to not more P0500, an issue that I think killed the transmission 10,000 miles ago with the previous owner and that has been a consistent intermittent issue for my whole experience fixing this rig up. Hopefully this finding can help someone else, for I wish this photo had been on a forum when I was searching. Thanks all for the good info [img]data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7[/img]