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Unread 09-01-2011, 06:16 AM   #1
Mistic
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Check Engine Light Code #15

How is everyone doing today? Throughout the past year I have been trying to clear up all the Check Engine Codes that are in my 1994 4.0L Computer since I have purchase the Jepp. Many many months ago I posted a thread asking for help diagnosing everything and trying to figure out why my CEL would trip after driving around after different periods of time.

That thread is found here...
http://www.jeepforum.com/forum/f12/o...ering-1108270/

I have finally narrow down the issue to Code #15 "No vehicle distance/speed sensor signal detected during road load conditions". My question is how can I go about fixing and/or correcting this problem.

A quick bit of info on my Jeep...it is a 1987 YJ with a 1998 4.0L Cherokee Engine and I believe matching transmission, however it has a 1994 Cherokee electrical and computer system. I know that this enigne swap is why the code is tripping and it probably will not do any damage, however that illuminated check engine light is starting to get anoyning and I want to fix the problem. Any suggestion and/or help is greatly appriciated.

Thanks!
Jay

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Unread 09-01-2011, 06:19 AM   #2
Mistic
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Also the transmission that is in my Jeep is either the TF999 or the 32RH, not sure if this is important to my issue or not. Thanks again!
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Unread 09-01-2011, 06:25 AM   #3
oldtime_ironman
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Do you have the 1994 Cherokee ECM? If so then I imagine its looking for the VSS input, and you would have to get one off a 1994. And put that in your t-case and wire it in.
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Unread 09-01-2011, 07:12 AM   #4
Mistic
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I do have the 1994 Cherokee ECM. My question is what is involved in installing a VSS into a transfercase that does not already have one? Is there a port there? Do I have to drill the T-case or is there something aftermarket that will make this easier.

I have also heard that I will need to change the cluster in the dash to a 1991 version so that I still have a mechanical speedometer but the electrical connection for the signal to the ECM is there too.

I'm just wondering is the VSS is needed in this case or does the signal read from the mechaincal speedometer and send it to the ECM that way?
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Unread 09-01-2011, 07:34 AM   #5
oldtime_ironman
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Quote:
Originally Posted by Mistic View Post
I do have the 1994 Cherokee ECM. My question is what is involved in installing a VSS into a transfercase that does not already have one? Is there a port there? Do I have to drill the T-case or is there something aftermarket that will make this easier.

I have also heard that I will need to change the cluster in the dash to a 1991 version so that I still have a mechanical speedometer but the electrical connection for the signal to the ECM is there too.

I'm just wondering is the VSS is needed in this case or does the signal read from the mechaincal speedometer and send it to the ECM that way?
Well, on my 1991 both the VSS and the speedo cable screw into the same plug, which then screws into the normal speedo hole on the T-case. So I imagine its just a matter of getting the VSS with speedo cable housing for a 1991 and screwing that into your normal speedo hole.

Yeah you will need a mechanical speedo tho. I don't think you would have to change the whole dash cluster, since the speedo on a 1991 comes out separately. Not totally sure bout that tho.

.
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Unread 09-01-2011, 08:16 AM   #6
Que89YJ
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You can do a quick search and come up with the threads dealing with the 91 VSS. The ECU needs the input from the VSS for acelleration and deceleration. The 91 and several other vehicles had the crossover sensor that had both mechanical as well as electronic. When you get it (scrap yards are the best place) get the connector, and speedo cable as well. the connector is a 2 wire instead of the 3 so you will need to splice it in.
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Unread 09-01-2011, 09:08 AM   #7
Mistic
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oldtime_ironman, thank you for your info this does help me some.

Que89YJ...I actually did come across one of your threads before when you were discussing this with brentd711. Actually that is how I knew about the 91 Cluster. However I'm still a little confused, and maybe because I'm not real certain on the components and setup with the VSS.

Correct me if I'm wrong guys...But the vehicle speed sensor (VSS) is a sensor that will connect into my current speedometer port on my transfer case with no modification. Then coming out of that VSS is the speedometer cable that goes up to my speedometer and one signal wire that I will need to splice so that I can run one to the new 1991 speedometer gauge (Which I will have to get) and one to the ECM. Is that correct or did I mixup something with the wiring. (or can I keep my existing speedometer that I have now and there is no signal wire that has to go up to the dash, only to the ECM which makes more sense to me) Also were or how do I tie into the ECM? Thanks!
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Unread 09-01-2011, 09:29 AM   #8
oldtime_ironman
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Quote:
Originally Posted by Mistic View Post
oldtime_ironman, thank you for your info this does help me some.

Que89YJ...I actually did come across one of your threads before when you were discussing this with brentd711. Actually that is how I knew about the 91 Cluster. However I'm still a little confused, and maybe because I'm not real certain on the components and setup with the VSS.

Correct me if I'm wrong guys...But the vehicle speed sensor (VSS) is a sensor that will connect into my current speedometer port on my transfer case with no modification. Then coming out of that VSS is the speedometer cable that goes up to my speedometer and one signal wire that I will need to splice so that I can run one to the new 1991 speedometer gauge (Which I will have to get) and one to the ECM. Is that correct or did I mixup something with the wiring. (or can I keep my existing speedometer that I have now and there is no signal wire that has to go up to the dash, only to the ECM which makes more sense to me) Also were or how do I tie into the ECM? Thanks!
Sort of. If you get a 1991 VSS then yes it goes into the normal speedometer port. Then the speedo cable for the existing mechanical speedo screws into the other end of the VSS. The signal wires from the VSS need to be spliced into the computer harness. At least that's how my stock 1991 is setup. So all you really need to know is where the wires will go. The rest of it is pretty obvious once you see it.

.

Last edited by oldtime_ironman; 09-01-2011 at 09:30 AM.. Reason: need to know
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Unread 09-01-2011, 09:41 AM   #9
lclark2074
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Hears a pic of the adapter

As you can see with the botom pic you will nead the right cable to make it fit but it dos work.
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Unread 09-01-2011, 09:45 AM   #10
Mistic
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Ok...This is good stuff!

Thanks for the pics lclark2074!

From what I'm reading else where, I will need to change my current speedometer cable to matchup with the sensor connection and get the adapter to step up the size of the cable at the speedometer, correct?

Does anyone know where to tie the wiring into the ECM? Is there a plug or do I need to cut and soldier?

Also how do I splice in the third wire to the two wire sensor?

I know that a three wire sensor has the 5-8v power supply, the sensor return signal and the sensor ground.
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Unread 09-01-2011, 09:47 AM   #11
Que89YJ
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You don't need a new guage. The 91 sensor is setup with a cable and sensor so you take the cable from the 91 VSS and put it into your guage like you have currently. The diffeence is it also has a connector coming off the side of it with 2 wires. It has 2 wires 1 wire goes to pin 47 on the ECU and the other to power like in this post: http://www.jeepforum.com/forum/f12/4...ection-963222/. The new VSS sensors were all electronic and had an output to the cluster from the ECU for speed. They also had a 3 wire sensor. You only need the 2 wires like in this post. It's easy to do.

Thanks Iclark.
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Unread 09-01-2011, 09:50 AM   #12
oldtime_ironman
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Quote:
Originally Posted by Mistic View Post
Ok...This is good stuff!

From what I'm reading else where, I will need to change my current speedometer cable to matchup with the sensor connection and get the adapter to step up the size of the cable at the speedometer, correct?

Does anyone know where to tie the wiring into the ECM? Is there a plug or do I need to cut and soldier?

Also how do I splice in the third wire to the two wire sensor?

I know that a three wire sensor has the 5-8v power supply, the sensor return signal and the sensor ground.
Dunno if you'll even need to change the speedo cable, you might not need to. HUGE thanks to lclark2074 for the pic - yes that's exactly what I mean.

You could tap the 5-8v supply off other sensors if needed - the MAP has one IIRC. On a factory setup there should be a plug, but I don't know because you had swapped things around - might have to figure that out.

.
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Unread 09-01-2011, 10:13 AM   #13
lclark2074
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Quote:
Originally Posted by oldtime_ironman View Post
Dunno if you'll even need to change the speedo cable, you might not need to. HUGE thanks to lclark2074 for the pic - yes that's exactly what I mean.

You could tap the 5-8v supply off other sensors if needed - the MAP has one IIRC. On a factory setup there should be a plug, but I don't know because you had swapped things around - might have to figure that out.

.
(pin 74 white with an orange tracer) vss input
(pin 4 black with an blue tracer) signal ground
If I remeber right the vss in computer makes enuff voltage to read the macanacal reed switch in the 1991 senser.
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Unread 11-08-2011, 06:40 AM   #14
Mistic
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Well everyone my Check Engine Light Code #15 "No vehicle distance/speed sensor signal detected during road load conditions" has been fixed this past weekend. I installed a new VSS for a 1991 Jeep and it worked perfect. It was actually easier then I thought it would be, the wiring in the Jeep was already converted to the two wire harness so all I had to do was switch out the old sensor with the new one. Problem Fixed! Thanks for everyones help!
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Unread 11-08-2011, 09:39 AM   #15
Que89YJ
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Mystic, did it make a difference in the other issue with charging?
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