Mechanics

JIMMY 4X4 4.3L WHEEL SPEED SENSOR

1993 GMC S15

On my 1993 Jimmy S15 4x4 4 door 4.3L CPI vortec, the ABS light always comes on and flashes a code 38, according to my book it is a left rear wheel speed sensor. I know there is one at each front wheel but I looked all over the back and can't seem to find it anywhere. If anyone knows where the rear wheel speed sensors on my truck are located I would really appreciate it if you can put me in the right direction. When I brake the pedal pulses and is hard to push then all of a suden it kicks in. That don't happen all the time though, only once in a wile during a drive. At the same time it happens you can hear a noise in the front end almost like a hydrolic pump sound trying to work. I would like to check my wires and clean the sensor before I spend hundreds at a service center. Once again I would appreciate any advice or help you can offer. Thank You
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Graywolf1750
September 18, 2007.




On the rear brakes if tou don't have sensors at each wheel you have RWABS look on the top of the differential, the electrical part is what you need to test, replace! Or the wires to it! Check the wire first, I use an ohm meter to check for resistance between the front of the harness to the rear. Should get between 800-1400 ohms.

Merlin2021
Sep 18, 2007.
As I looked all around the rear end, I could, t find anything that has wires. I looked around the rear differential as well as the backing plates. If my truck doesn't have the 4WAL system why would I get a code 38 from the 4WAL trouble codes? I will double check the diff again. Thanks for your information.

Tiny
Graywolf1750
Sep 18, 2007.
I have double and tripple checked the rear differential for the speed sensors and there is none, I also rechecked the rear backing plates and I can't see them there either? Man this is frusturating because I know they should be there somewhere be I just can't seem to find them and I know my truck has 4 wheel anti lock brakes. PLEASE SOMEONE HELP ME FIND THE LOCATION. Thanks
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Tiny
Graywolf1750
Oct 15, 2007.
I believe 93's if they had any sensor, it's mounted on the TOP of the differential, If you see something up there with an electrical connector, you found it!

Merlin2021
Oct 15, 2007.
There is nothing there but the breather vent hose. This is what is confusing to me because I gave my VIN number to the dealer and they also tell me that it is a 4wal system. And the code 38 that flashes me is also a 4wal code and not a rwal code. Would there be any other place it could be like maybe the transfer case or something like that? Because There not on the rear backing plates either.

Tiny
Graywolf1750
Oct 15, 2007.
I just went out to check the transfer case, At the front or the rear driveshaft there is a housing that connects to the transfer case. At the top of that housing there is a electrical connector that connects to something that looks like an oxygen sensor. Could this be the rear speed sensor? Thanks

Tiny
Graywolf1750
Oct 15, 2007.
I searched the rear end for hours and the only things that are on the rear diff is my emerg brake and brake lines, they run across. On the backing plates on the rear has only the emerg brake and the brake line coming out of them. When I jump the wires as to the hilton book, my abs light flashes 3 times and then 8 times which is a code 38. The book says it is a left rear wheel speed sensor. I also looked on the net and the gm code reader says the same thing, but for some reason I can't seem to find it in the back at all. I can't even find the spot where one would go. Would it be located somewhere else besides those two locations as I can't find it if my life depended on it. Well I guess my life does depend on it when I think about it. Well PLEASE anyone with any ideas or sugestions would be greatly appreciated. Thank you

Tiny
Graywolf1750
Dec 4, 2007.
Are there any sensors on the front wheels? If not you most likly don't have ABS. Look under the Master cylinder, is there a box with brake lines and wires there?

Merlin2021
Dec 4, 2007.
Yes there are front sensors that are at both front wheels. I seen them when I removed the rotors to replace them. They run on what looks like a sprocket. I do have a aluminum box under the master cylinder that connects to the brake booster and there is 2 lines from the master (where you top up the the fluid) to that box and there is 1 wire that runs from that aluminum box. The wire is a tan colour with a white line. I'm not sure where it runs to as it goes into a black wire protector alongwith other wires from other components. Is that wire for the rear sensors? Could that conection be the problem? Does this help you in trying to help me locate the left rear speed sensor? I appreciate you taking the time to help me with this. Please let me know as soon as you can. Thank you so much. Hope to here from you soon.

Tiny
Graywolf1750
Dec 5, 2007.
No if it's only 2 lines its just a junction block, branches out the two front brake lines. The control box I.M looking for will have an electrical connector with perhaps 10-20 wires on it, and steel lines in and out. Not just 2 but 8 lines.I will try looking it up one more time. Do you have the prodution date? It will be on a sticker on the drivers door jamb.

Merlin2021
Dec 5, 2007.

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