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1995-2002 Range Rover P38A
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Discussion Starter #1
I am still troubleshooting my transmission's lack of an output shaft speed signal, and one of the things that I have come across a couple of times is how important the screen on this cable is.

Output Shaft Speed Sensor –pins 2, 38, 20​
The automatic gearbox system incorporates an​
output shaft speed sensor which is input to the Auto​
Gear Box Control Unit (Z255) on pins 2 and 38 with​
a screen over the cable attached to pin 20. It is
important that this signal is screened correctly.

I have visually inspected this cable, it just looks like a thicker wire. I can see that the screen is supposed to be attached to pin 20 at the transmission computer, what about the other end? I am sure that I am missing something basic with what it means to check on this screen. What are the measurements I should be making and where should I be making them to evaluate the screen's integrity.
 

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Premium Member
1970-1995 Range Rover Classic
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455 Posts
The other end should go to earth.
If you jack up your car to test the sensor, do you get any signal between the housing and the pin?

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1995-2002 Range Rover P38A
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31 Posts
Discussion Starter #3
Thanks Annette!!

I do not think I got good results. First off the blurb I copied above does not match the pinout on my truck, I have the Bosch controller and used that pinout for the measurements below. Here are the numbers I have:

This is the measurement from the bell housing on the transmission to Pin 15 - Output speed sensor screen



8.48 MOhms. I did not even think I was getting continuity when I first tried to measure this.

For comparison I also measured from the bell housing to Pin 6 - Power ground and got:



1 Ohm, I was using a clamp on the bell housing and did not move it so I feel pretty sure that there was a pretty good connection there.

Finally, for reference this its the measurement from Pin 14 to Pin 42, which connect to the sensor itself.



That is on a brand new sensor and it matches the measurement from the "bad" sensor I just replaced. The diagnostic decision diagram in Rave suggests that this measurement should be 1050 Ohms. All the other references that I have found online suggest that the 315 Ohm value is correct for this specific sensor. I cannot explain that.

At this point my question is should the shielding connection have that much resistance? I am thinking know, but then again maybe it is like ignition wires where you want high resistance for design reasons.
 

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Premium Member
1970-1995 Range Rover Classic
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455 Posts
[ I am green with envy, what a fine multimeter : ) ]

Here are 2 observations..
In the 1999 manual screen is not earth.. maybe they forgot to mention it, but it was only when I was digesting your post after dinner that I noticed (sorry couldn't do it @work). See the picture and pages 15 vs 17 of the English manual.

May I suggest you check pin 15 against 28?

Did you check the continuity f the screen across c0745. That would be a great suspect.

And compare to the screen on the transfer output sensor.. as seen in the second pic this one actually goes to earth


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Premium Member
1970-1995 Range Rover Classic
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455 Posts
I just had an idea..
Recently, I noticed on a Mexican market Disco td5 that they had different plugs, just like p38 v8 NAS ones. I was struggling with random shifts and trying to repair the plug.
(B) was loose and (H) was intermittently touching screen.

I fixed it in the end with a second hand cable from a p38 like yours. Made 1 out of 2.

Check that plug inside out.
And keep the 'old" sensor



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1995-2002 Range Rover P38A
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31 Posts
Discussion Starter #6
I really appreciate this help. I started puling console to get to that connector, I'll let you know what I find later this evening when I get in there after work.
 

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1995-2002 Range Rover P38A
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Discussion Starter #7
I was able to test the continuity from the computer to the connection under the center console. I was able to get continuity on all three conductors with generally 3 Ohms of resistance. I was able to get it down to 0.3 Omes if I was really careful the probes. I suspect that indicates some oxidization on the plug connectors. I tried to undo the plug at the transmission but I was not quite sure of how it connected and did not what to force it. I assume that I need to twist the base and it will disengage? I wanted to ask before I forced it and broke it.
 

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1995-2002 Range Rover P38A
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31 Posts
Discussion Starter #8
I might have a source for a second transmission computer. It would be easy to swap out of the one i have in case that is the source of my problems. Can I just do that or is there some coding that I have to do to make the truck recognize the new computer? I do have a Nanocom if that would help.
 
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