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Vincent, Ford Senior Master Technician
Category: Ford
Satisfied Customers: 1450
Experience:  28 years as Tech.
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Have a 1999 RV on a Ford F53 chassis, V10, 6.8L engine.

Customer Question

Have a 1999 RV on a Ford F53 chassis, V10, 6.8L engine. Transmission has started shifting hard (no smooth shifts). The scan tool gave me a code (don't have number) indicating "speed sensor erratic/hi (A). Talked to local for parts department, they say this chassis only has a rear sensor for speed, ABS and transmission control. The shop rep says it has two sensors. The rear on controls ABS and speedometer and the one on the transmission controls shifting. Can anyone clarify this before I waste my time trying to get the right part.
Submitted: 9 years ago.
Category: Ford
Expert:  Vincent replied 9 years ago.

If you give me the actual code that will help. There is a speed sensor mounted in the differential that the transmission uses, but there are also more then one speed sensor on the transmission. On your vehicle there are 3 speed sensors on the transmission.

Knowing the actual code will let me tell you which direction to head.

Customer: replied 9 years ago.
Hi Vincent...I do not have the scan tool with me to read the history....It was something like a P758   708 or something which really does not help. I can forward that information but it will be around 6PM Dallas time. I had this problem in Seattle about 5 years ago who works for Ford got the part and replacement...I thought it was on the rear, but I was not there when he did it
Expert:  Vincent replied 9 years ago.
That is not a problem. I would much rather give you accurate information, then guess.
Customer: replied 9 years ago.
OK Vincent...I had my wife pull out my notes from the motorhome and she says the code is P030....possibly 031...I wrote it pretty fast last night

Aa very outside chance the 3 is a 5 but she is pretty sure it is a 3
Expert:  Vincent replied 9 years ago.

There are over 200 possible diagnostic trouble codes for that vehilce. Do we really want to guess what the code is?

I am looking for a 4 digit code with a letter in front. The codes will read like P0301, P0758, something along those lines.

P03xx codes are always misfire codes and will have nothing to do with speed sensors.

Remember the more accurate the information is that I get, the more likely that we will fix your truck.

Customer: replied 9 years ago.
Hi Vincent...well, my wife isn't blonde and I have terrible handwriting so I cannot blame it on her. I still thik it had a 5 and 7 in it probably prececed by a zero...but I need to check myself. I will send the code out of the scan tool if it is still stored. If not, I am doing other work on the rig that will prevent me from driving it again for a few days...if so, I will probably pull every sensor I can find iin the tranny and rear end and replace all of them....I will definately get back to you and square my payment before doing anything else...thanks for your patience

Expert:  Vincent replied 9 years ago.

Why would you replace every sensor on the transmission? If you hae a NON-Transmission code you will just be throwing your money in the garbage can. Before you throw any part at the vehicle, just get me the code. The transmission can be shifting harsh, because of an engine sensor or a misfire. If the engine control computer detectes a fault in any system, it will crank up the transmission shift pressures to protect the transmission.

And what happens if the code that you have is a "torque converter excessive slippage" code? Do you really want to spend several hundred dollars on a bunch of sensors that will not fix your problem?

Please, PLEASE do NOT just throw parts at a vehicle. I cannot stress this enough. Get me the code and lets fix the vehicle correctly. A couple of more hours will not hurt either of us and will save you much money.

Vincent and 2 other Ford Specialists are ready to help you
Customer: replied 9 years ago. have helped and i will provide positive feedback. But tell me, can I get back to you with the code somehow later with you? I would not expect that you would be working on line 24/7, but I would like to finish this question with you

Please advise
Expert:  Vincent replied 9 years ago.

Like I said, when you are ready. I am not in a hurry, and even if you send me the information to me when I am not online, no one else will get involved in the question.

As soon as I log back in, the question will be brought to my attention.

Customer: replied 9 years ago.
That is good. If I accept now does this close you out where I cannot get back to you. Or should I wait until you get the code and provide the answer.

Believe me Vincent, payment is not a problem...but I need the answer.

Expert:  Vincent replied 9 years ago.

Either way will work. But I don't have a problem with waiting for you to accept later.

Customer: replied 9 years ago.
Thanks...and I do not have a problem waiting for the answer until sometime tomorrow


Expert:  Vincent replied 9 years ago.
Customer: replied 9 years ago.
Vincent, The code on the speed sensor has to be either P0500 and more specific P0503
Expert:  Vincent replied 9 years ago.


I don't know if you understand. I know what the codes are for the speed sensors. I need to know what the codes were that your truck is throwing out.

Is the computer outputting the P0500 or the P0503? We really need specific information here.

However, both the P0500 and the P0503 refer to intermitant loss of VSS signal. That sensor is the one in the rear axle housing.

Customer: replied 9 years ago.
The message I got with the error code was

"Speed Sensor Erratic/High (A)

I am pretty sure it will be on the rear as my nephew change it out about 6 years ago and I am sure he climbed under the rear axle.

Thanks for your help and patience Vincent and I am sorry I took so much of your time.


Expert:  Vincent replied 9 years ago.


You did not take up a lot of my time and besides: That is why I am here.