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ABS Light P0500 & No Speed O

Radioace318

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November 22, 2011
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City, State
Shreveport Louisiana
Year, Model & Trim Level
1999 Exp XLT 5.0 2WD
The saga continues.
99 exp xlt 5.0 2wd auto trans.

Replaced (what I was told is the vss) on the 3rd member.
Replaced both wheel speed sensors on front.

Still ABS light on all the time. Check Engine Light comes on at highway speeds only. OBD II reports P0500

Never had a problem with shifting, OD is not a problem. It runs fine.

I sent this problem to one of those pay for an answer sites. Here was my question and reply(s)

"I have a 99 Explorer XLT 2WD. I replaced the sensor on the 3rd member and both front wheel speed sensors. I still have the ABS light and OBD II Code P0500. and NO Speed-O. What should I do next? A bad module maybe?"

answer:

"My reference material shows the VSS on the side of the transmission. This is the sensor that sends signals to the ecm for the speedometer and odometer. In the overhaul instructions in my reference, it's also called the output shaft speed sensor.

Different sized tires from what the vehicle came equipped with will cause the speedometer and odometer to read incorrectly but as far as I know shouldn't cause the fault code you're experiencing.

Tiny Answered by rivermikerat (expert)
1,052 answers provided "

Keep in mind this was the Free Ask area of the service.


ANy ideas anyone?
 



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So you replaced the sensor on the rear differential?

EDIT: I just googled "3rd member", I was not familiar with that term...so that answers my question.

I suppose it could be a wiring problem to that sensor.
 






So you replaced the sensor on the rear differential?

Yes Sir.

The one just to the top of the drive shaft and both on the two front wheels. Dude on the ask me web service tells me the vss in on the tail shaft of the transmission. I crawled under and found a small plate over where the old style speed cable would connect. Nothing connected to it except that little cover plate.

I think I may have confused the vss with the wheel speed sensors. I assume this is two different things so I replaced all 3 sensors. (two on the front wheels & one on the 3rd member)

I did see however a mass of wires connected to the transmission. Unless I overlooked it, I found NO sensor on the transmission.

My little ODB II tool cost me about 60 bucks 4 years ago. I do not get the information as to what sensor it is, just a P0500 (VSS Sensor A Malfunction)

I must be over looking something somewhere. May have a bad module? I'm at the end of my rope here.

Cheers
Rick

PS: I might add, After replacing the sensor on the 3rd member I drove around the neighbor hood never getting over 30mph or so. Should I take it out on the highway to 60 or 70mph and try to give the computer time to "re-learn" (for the lack of a better word) the system is working correctly?

My check engine light WILL NOT come on at slow speeds. Only at highway speed will it come on and return a code of P0500,
 






Rick, so you clear the code with your scanner after sensor replacement, and then the light comes back on?

PS: It is my understanding the sensor on the 3 member is VSS and ABS combined. The sensor on the transmission is the OSS (output shaft speed) sensor and is not used for ABS or speedometer.
Can you check voltage at the harness connector for 3rd member sensor?
 






Rick, so you clear the code with your scanner after sensor replacement, and then the light comes back on?

Exactly.

I reset the light and will come back on at highway speeds 3 or 4 minutes later.

The ABS light is ON all of that time. Can not get it to go out even with a "clear codes" command. That turns off the check engine light only.
 






I am however trouble shooting ODB II code P0500 (on another thread) I have replaced all three sensors (2 on front wheels & 1 on the differential) to no avail. One web site service tells me the vss is located on the tail shaft of the transmission. BS, Not on this ride.

Rick
 






I am however trouble shooting ODB II code P0500 (on another thread) I have replaced all three sensors (2 on front wheels & 1 on the differential) to no avail. One web site service tells me the vss is located on the tail shaft of the transmission. BS, Not on this ride.

Rick

If it is a 8.8, the VSS sensor is on top of the rear end on the front side above the pinion input. There is a wire running to it. Unplug it and take the one screw out and pull the sensor out. Try cleaning it up and replacing it and see what it does. Before you restart and try it out, reset the ECu though so you are starting fresh on the readings.

PO500 Veh Speed Sensor A malfunction-

A code P0500 may mean that one or more of the following has happened:


* The Vehicle Speed Sensor (VSS) is not reading (functioning) properly
* There is a broken/frayed wire leading to the vehicle speed sensor
* The vehicle's PCM is not correctly configured for the actual tire size on the vehicle
 






If it is a 8.8, the VSS sensor is on top of the rear end on the front side above the pinion input. There is a wire running to it. Unplug it and take the one screw out and pull the sensor out. Try cleaning it up and replacing it and see what it does. Before you restart and try it out, reset the ECu though so you are starting fresh on the readings.

PO500 Veh Speed Sensor A malfunction-

A code P0500 may mean that one or more of the following has happened:


* The Vehicle Speed Sensor (VSS) is not reading (functioning) properly
* There is a broken/frayed wire leading to the vehicle speed sensor
* The vehicle's PCM is not correctly configured for the actual tire size on the vehicle

Thanks for the heads up. What is 8.8? The module?
 






Thanks for the heads up. What is 8.8? The module?

The rearend, that is the size of rear axle housing you have in that Explorer. So on the VSS it should be on the top of the rearend in front above the pinion. You will see it, it has a plug going to it with 2 wires or one wrapped. The VSS is reading the rotation of the hone ring that is attached to the back side of the ring gear. But if you increase or change the tire diameter then it throws the VSS in a tissy because it can not read the proper speed due to the different tire size. Also they sometimes get caked up with grime on the end of it that is exposed to the oil and grime in the pmpkin, sometimes you can just clean the sensor up and it will read again. The sensor can be bought at any auto store for cheap too.
 






The rearend, that is the size of rear axle housing you have in that Explorer. So on the VSS it should be on the top of the rearend in front above the pinion. You will see it, it has a plug going to it with 2 wires or one wrapped. The VSS is reading the rotation of the hone ring that is attached to the back side of the ring gear. But if you increase or change the tire diameter then it throws the VSS in a tissy because it can not read the proper speed due to the different tire size. Also they sometimes get caked up with grime on the end of it that is exposed to the oil and grime in the pmpkin, sometimes you can just clean the sensor up and it will read again. The sensor can be bought at any auto store for cheap too.

Oh That is the 8.8 info. Well, That was the first thing I did was to make sure all the wires & connections were nice and clean. I did remove the vss and cleaned it up to. That did nothing to address the issue.

That is when I ran down to the local Advance Auto and picked up a new vss and installed it. Still, No Joy.

Then I checked both front wheel sensors with a VOM (Volt Ohm Meter) and found 1.8K on the left side wheel and 1.9 on the right. Did the spin the wheel test and found small voltage on each.

I replaced them too. Still No Joy. I did take note when I bought the suv it had 235/15's on the rear and 205/15s on the front. I may be running in circles here.

Thanks
Rick
 






I did take note when I bought the suv it had 235/15's on the rear and 205/15s on the front. I may be running in circles here.

Thanks
Rick

What is the middle number on the front and rear tire size?

If you are running 2 different size tires front and back, that should be the culprit there in itself, if the diameter is way off. The front sensors are reading one RPM and the rear VSS is reading another. You need the front and rear to be the same diameter in all. The sizes (width) can be different as many of us have done so in the past or present. But the overall diameter needs to be the same. This points directly to the 3rd bullet in the reasons I posted to you previously.
 






What is the middle number on the front and rear tire size?

If you are running 2 different size tires front and back, that should be the culprit there in itself, if the diameter is way off. The front sensors are reading one RPM and the rear VSS is reading another. You need the front and rear to be the same diameter in all. The sizes (width) can be different as many of us have done so in the past or present. But the overall diameter needs to be the same. This points directly to the 3rd bullet in the reasons I posted to you previously.

Think you may have hit the nail on the head here. Just went out to the garage to read the sizes of all the tires.

The front has 205/70/15s. The rear has 235/75/15s

Of course the front tires are doing more RPMs than the rear. This could be my problem. I have checked and changed everything I could think of.

Too bad my little Actron scanner did not tell me what all to look for. It was/is just reporting "Sensor A VSS malfunction.
 






The front has 205/70/15s. The rear has 235/75/15s

205/70/15= 26.3" height, section width 8.1", section height 5.7"
235/75/15= 28.9" height, section width 9.3", section height 7.0"

First set of numbers, 205 and 235 equals the width of tread in mm's

Second set of numbers- 70 (section height), equals 70% of the 205mm's tread width from rim lip or bead, to the top of the tire, 75 equals 75% of the 235mm's tread width from the rim lip or bead to the top of the tire.

Third set of numbers 15 is the rim diameter

The section width is the width from sidewall to sidewall.

The difference in both these tires is hugh when it comes to the ECU trying to compute what the VSS in the rearend is reading and the speed sensors up front are reading and the two are not compatible to one another. I bet that is your whole issue.

You need to get the same diameter matched tires for the front and rear, one way or the other. Like I said before, you can plus size tires, but the overall diameter needs to be relatively the same within a couple 16th's of a inch.
 






I read somewhere .25" is the tolerance, so that set is badly mismatched.
 






I read somewhere .25" is the tolerance, so that set is badly mismatched.

wow! Just 0.25 to play with? Looks to me like just a low tire would flag the light in some cars. Should you have to use a do-nut spare in some cars would screw with your head.


Rick
 






A low tire doesn't change circumference much, if any.
 






wow! Just 0.25 to play with? Looks to me like just a low tire would flag the light in some cars. Should you have to use a do-nut spare in some cars would screw with your head.


Rick

A donut spare is usually the same diameter as the original supplied tire on vehicle, it is just way skinnie and meant for low speed driving temporarily. It does not take much to throw off the VSS and speed sensors in order to throw a CEL. In your case specifically, the difference in diameter from front to rear is almost 3"s which equates to 1.5" in sidewall height. Which is hugh witha computer managed vehicle.
 






Your mismatched tires are most likely the issue. For a minute, I thought you had the 5.0 AWD, in which case the mismatched tires would be an even larger issue.

I can explain why the code reader was unable to give you more detailed information. The ABS light being on is the key - this indicates codes are present in the ABS module, which cannot be read by a conventional code reader. If you attached a reader with ABS capabilities, you would most likely get an error in the format Cxxxx rather than Pxxxx. In your case, the problem is so bad that the ABS module is sending bad (or no) speed information to the PCM, thus triggering the P0500 code.

After resolving the tire issue, you should swing by Advance Auto Parts, or somewhere else that has readers with ABS capabilities and have the codes cleared (AAP is the only place in my area that has ABS capabilities on their free scanner).
 






Finding a free scanner with ABS capability may be very difficult. Unhooking the battery for 20+ minutes may get the light to go out but the code should still be stored. Not that really matters.

That answer site gave you info for a pre 97 Explorer. As you have found, the speedometer/ABS rear sensor is combined on the rear third member.
 



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Update:

New VSS on read end
Both front wheel speed sensors replaced with new ones.
All 4 tires & wheels are the same size now and all correct air pressure

Removed battery cables for over 6 hours in an attempt to reset all modules.

I recall what Joecrna said:

"I can explain why the code reader was unable to give you more detailed information. The ABS light being on is the key - this indicates codes are present in the ABS module, which cannot be read by a conventional code reader. If you attached a reader with ABS capabilities, you would most likely get an error in the format Cxxxx rather than Pxxxx. In your case, the problem is so bad that the ABS module is sending bad (or no) speed information to the PCM, thus triggering the P0500 code."

This seems to be correct. My Actron CP9135 code reader will only delete the P0500 vss malfunction error. It will NOT reset the ABS light or show ANY ABS codes at all.

I did verify all the wiring and connections are in good working order. (short of ohming out from the module to the sensor locations)

I did note today my auto door locks will engage the second I start moving. NOT when I shift from Park to Drive or Reverse. The suv HAS to be moving in order for this to happen. THAT tells me it is getting a sense of movement from somewhere. Could be the VSS or the WSS's on the front. I do not know for sure.

I also noted the am/fm radio DID NOT lose the memory even after the 6 hour absence of B+

So it is off to the local parts house with an ABS scanner to see what I learn from that.

Thank you all so much for your input. It is very appreciated.

Cheers
Rick
 






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