I'm stumped. The ABS light came on, along with a check engine light. The speedometer still functions and the auto-tranny shifts fine. I put a code scanner on it and there are no codes. The wife noticed the other day that when she started moving from a complete stop she saw the needle "pop" from 0 to a bit over 20mph than "settle" back to 20mph (which was the posted speed limit.)

She drives a '99 2WD with automatic transmission that has less than 24,000.

any suggestions are welcome. I'm fixing to take it for some test drives with the scanner on to get a better reading of what is going on.

Thanks.

 

Is it just RABS, or is it 4WABS????

With the speed-o acting out & the ABS light on, kinda makes me wnt to suspect the rear differential speed sensor.

Not sure about the CEL, if it came on, & has stayed on, then seems to me to me there should be a hard code set.

If the CEL came on, but then went off, seems to me there should be a pending code stored.

Good idea imo to take it for a test drive with the scan tool hooked up.
Let us know what you find.

 

I cleared the CEL and it has not come back on yet. It is 2WD and i think it is just RABS. I found a part replacement for the possibly defective sensor. It is a part that belongs on a '97 F150 which fits in the rear differential. I have no speed sensor on the tranny and all the part stores tried to sell me a sensor that is supposed to fit in the tranny with a pass through for the speed cable. I have no speed cable that I can see, which leads me to believe the system is electronic. But I did remove the original part and took it with me to the store. The clerk did his best to find the part and when he did, he said it was listed for the '97 F150's. Go figure, sorry to say that it will be Monday before I can get the part and put it in.

 

The part that most stores tried to sell me looked like this.



The part I need looks like this.



EDIT:
Actually I just found this through the one stores online parts section. It is exactly what I need. Why could they not find it? I hope this will solve my problem.

 

Yes your speed-o is electrically driven & it also takes clues from the rear differential speed sensor.

It's probably a nomenclature problem, with them not being able to find the speed sensor listed.

I think it's listed as a ABS speed sensor, so if they were looking for it under parts listings for the speed-o, they probably wouldn't find anything listed unless it was cross referenced.

If the speed sensor part #'s are the same, it should work.

Maybe you had/have two problems & the CEL was a coincidence!!!!????

What did the test drive with the scan tool hooked up, show????

 

I didn't get the chance to run it with the tool hooked up yesterday. The CEL has not come back on yet. Since the shift from 1st to 2nd is so hard, I will take the car in to the parts store today to see if they got the right part in this afternoon. I really don't want to tear up the transmission in the truck. I know it's probably nothing, but better safe than sorry.

If it's not the right part comming in today, I have the other store in town getting the correct part and that will be in on Monday.

 

OK, if you are also having auto tranny shift problems, at the same point the speed-o is acting out, along with the ABS warning light, it's just another clue pointing to the rear ABS speed sensor. They are a common problem part.

The ABS system & computer uses the speed sensors output in figuring out what the vehice is doing & what it is being asked to do by the driver.

The engines computer uses other inputs, along with this speed sensors out put, to also decide when the tranny should shift, so if the speed sensors output is corrupt, the computer gets confused & rough shifting can result.

Seeing as how it's a low speed shift problem & the speed-o is also acting up at low speeds, it sure sounds like that that pesky speed sensor should be high on your suspect list.

On Edit: Seeing as how your down in hot humid Fla. & if your also close to the beach where this ride is exposed to salt spray, I'd carefully check the speed sensor & it's electrical connectors pins & sockets for corrosion & any physical damage.

 

Well the correct part came in today. needless to say, 5 minutes under the truck was all I needed. ABS light is now off, CEL light is now off, and the transmission shift from 1st to 2nd is feeling normal.

I did put the scan tool on it on the trip to the parts store (before repair). All perameters were reading normal except for the speed reading. It would sit at 0 then jump to 20. After replacing suspected part, I took it for another drive with the tool. All is functioning within perameters.

Hope this thread will help others. Thanks for the input pawpaw.

 

OK, good touble shooting, find, fix & feedback. Good idea to road test that puppy with the scan tool attached & verify the speed sensor was indeed acting up, before throwing a part at it.

Good to hear it was that simple & your "on the road again"!!!!

I had a very silmilar shift problem with my 94 Taurus & it's speed sensor. My speed-o was cable operated, so I didn't have the luxury of having it being an electronic speed-o readout, so that I could see the speed-o acting up. Also didn't have any CEL & it doesn't have ABS & there were no pending or hard trouble codes set.

The only way I caught it, was to hook my Actron CP9150 scan tool kit up & have the wife drive it, while I monitored the speed sensors PID output to the computer. Mine was erratic around 30-37 mph & it was screwing over the 1-2 & 2-3 up & down shifts. Sometimes on the up shift, it felt like I was "slam shifting" the dang thing & on the 2-1 down shift, sometimes it would grab 1'st & squeel the tires. Everyone thought the tranny was kaput!!!!!

Scantool PID's said nope, the danged speed sensor is acting out. That one find alone, paid for about 1/3 the cost of the scantool.
Just gotta love these dang things!!!!

Anyway danged good use of your scantool, to verify the problem, before any expenditure of your gold!!!! lol