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Unread 10-08-2011, 03:27 AM   #1
DavidJames27
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1990 XJ Cherokee 
 
Join Date: Oct 2011
Location: Yakima, WA
Posts: 13
tranny doesnt shift on its own...

I have a 90 cherokee 4.0 automatic that will shift just fine through all gears manually using the gear selector but will not shift up or down from any gear automatically, if anyone knows what might be the problem i would appreciate it thanks

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Unread 10-08-2011, 06:29 AM   #2
tjwalker
It's the crank sensor!
 
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1999 XJ Cherokee 
 
Join Date: Nov 2007
Location: Central Minnesota, MN
Posts: 8,517
First thing to do is to verify the throttle position sensor. Directly involved with shifting of the AW4. Here is more.
--------------------------------------

RENIX TPS ADJUSTMENT

Before attempting to adjust your TPS be sure the throttle body has been recently cleaned.
It's especially important that the edges of the throttle butterfly are free of any carbon build-up.

IMPORTANT NOTE: Using one lead of your ohmmeter, probe the B terminal of the flat 3 wire connector
of the TPS . The letters are embossed on the connector itself.
Touch the other lead of your meter to the negative battery post.
If you see more than 1 ohm of resistance some modifications to the sensor ground harness will be
necessary. The harness repair must be performed before proceeding.
I can provide an instruction sheet for that if needed.

MANUAL TRANSMISSION:

RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body.
This manual transmission vehicle TPS provides data input to the ECU. The manual transmission
TPS has three wires in the connector and they're clearly embossed with the letters A,B, and C.

Wire "A" is positive.
Wire "B" is ground.

Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors..
Note the voltage reading--this is your REFERENCE voltage.

Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your
OUTPUT voltage.
Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For
example: 4.82 volts X .17=.82 volts. Adjust the TPS until you have achieved this percentage. If
you can't achieve the correct output voltage replace the TPS and start over.

AUTOMATIC TRANSMISSION:

RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a three-
wire connector, same as the manual transmission vehicles have, and it is tested the same as the
manual transmission equipped vehicles--FOR ENGINE MANAGEMENT RELATED ISSUES.

However, the automatic TPS also has a four-wire connector clearly embossed with the letters
A,B,C, and D.. For the automatic transmission equipped vehicles the four-wire connector
provides data to the TCU.

Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your
REFERENCE voltage.

Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT
voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage.
For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage.
If you can't, replace the TPS and start over.

So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and
the other side feeds the TCU. If you have TRANSMISSION issues check the four-wire
connector side of the TPS. If you have ENGINE issues check the three-wire connector side of
the TPS.

For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is
stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
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Unread 10-08-2011, 06:32 AM   #3
Azzy
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1996 XJ Cherokee 
 
Join Date: Sep 2010
Location: Finleyville
Posts: 3,238
Could be a couple things.

I would give this a read, and check it out. I have the same issue, caused by a bad connection or a bad engine speed sensor (not sure yet)

http://www.transonline.com/transdige...ers/index.html
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Unread 10-08-2011, 07:39 AM   #4
cruiser54
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1990 MJ Comanche 
 
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Location: Prescott, Arizona
Posts: 10,322
First place to look is up under the passenger side dash, below the glovebox. The Trans Control Unit, aka TCU, is located up there. It has an inline fuse wrapped in some yellow tape. If that fuse is blown or the socket is corroded you will have your exact symptoms.
As Mr Walker suggests, the TPS is suspect here. Test the TPS on the Trans side per his instructions. Takes a few minutes and then you'd know for sure.
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Unread 10-09-2011, 12:46 AM   #5
DavidJames27
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1990 XJ Cherokee 
 
Join Date: Oct 2011
Location: Yakima, WA
Posts: 13
Thanks guys, it turns out the whole wiring harness under the glove box wasn't plugged in to the silver box there which I am assuming is the TCU since it solved the problem. I never would have thought to look up there on my own so thank you very much.
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Unread 10-09-2011, 08:33 AM   #6
cruiser54
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1990 MJ Comanche 
 
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Location: Prescott, Arizona
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Did you just acquire this Jeep?
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Unread 10-10-2011, 01:00 AM   #7
DavidJames27
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1990 XJ Cherokee 
 
Join Date: Oct 2011
Location: Yakima, WA
Posts: 13
yeah, I just bought it from my brother who replaced the steering column a while back and i guess he forgot to hook that back up when he put the dash back together
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Unread 10-10-2011, 06:29 AM   #8
cruiser54
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1990 MJ Comanche 
 
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Location: Prescott, Arizona
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Okay. That makes sense.
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Unread 10-10-2011, 07:43 AM   #9
Azzy
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1996 XJ Cherokee 
 
Join Date: Sep 2010
Location: Finleyville
Posts: 3,238
Wow, you lucky bastidge!

Glad to hear it is fixed
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