I have been having weird problems with my overdrive & no backup lights.

This all started about a year ago when i noticed my overdrive had stopped working, although pushing the button on the dash did turn the indicator on & off.

After some research I discovered the "black box" on the right hand side of the glove box. This box interfaces the OD button with the OD switch circuit. Each time you push the button it toggles the outputs on or off. This module is connected to the wire from the PCM which goes through the temp sensors next to the trans.

This test information assumes you have a known good TPS or a Known good pot installed to replace the TPS.


The wire color codes & functions on the module plug are as follows:

Yellow/Black . . . . . . . To OD switch
Black . . . . . . . . . . . . Ground
Orange/White . . . . . . OD on signal to PCM
Blue/White . . . . . . . . Power
Orange/Yellow . . . . . . Overdrive off indicator lamp (inside switch)
Yellow/Blue . . . . . . . . To OD switch

To test this system, unplug the module from the harness.
These tests are performed with the KEY ON.

Test for power & ground by connecting a test lamp from BLACK to BLUE/WHITE wires with the key on . .if it lights power is good. If not, check fuse 12. If fuse is good probe BLUE/WHITE with grounded test lamp. If it lights this way, you have a bad ground wire.

Using a grounded test lamp, probe the ORANGE/YELLOW wire. The OD off lamp should light.

Using a continuity sensor, test YELLOW/BLUE to YELLOW/BLACK. The continuity sensor should only show continuity when the OD button is pressed.

If these tests are all good, jumper BLACK to RED/WHITE and go for a drive.
If the OD works normally, the control module is bad.
If it still does not work, test the temp sensors, if they are bad the signal will not reach the PCM.
If the temp sensors pass, ground the ORANGE/LIGHT GREEN wire from the OD plug (PCM pin 55). Test drive the vehicle. If OD now works you have a wiring problem

Assuming all of the wiring tests pass & you can jumper OD on from the module plug, replace or repair the module.

This module is PN 56003275 and was available from Chrysler for about $50.00 the last time I checked.

I will explain how to repair the module in a later post.

 

Hmm. Have you tried to manually ground out the o.d selinoid. It sounds like your switch is working fine. Sounds like you have a bad tps or a maybe a faulty o.d selinoid.

 

I drove my truck for nearly a year with my OD simply jumpered at the module plug before i finally got around to doing this. During this time I noticed that on cold, wet days my OD would intermittently cut in & out and my backup lamps did not work. The OD would randomly kick in & out even with the jumper removed to disable OD!!

When I got under the truck to check things out I found the overheat sensor wiring was rubbing on the neutral/Back UP lamp switch wires and had worn through the insulation on both.

The trans temp sensor is the one in the trans cooler pipe with the RED/WHITE & ORANGE/BLACK wires on it.
The Neutral swith is the one on the side of the trans above the pan. It will have 3 wires on it.

These wires are:

White . . . . . . . . . Back up lamp power from fuse 13
Brown/yellow . . . . Neutral switch
Violet/Black . . . . Back up lamp switched wire

When I check mine I found the WHITE wire contacting both temp switch wires. This blew fuse #13 and was randomly engaging OD.

After repairing this problem and installing a new fuse for the lights my OD worked as expected. (I bypassed the overheat switch thinking it was the low temp switch)



Now that i have explained how I fixed the short circuit that probably destroyed my OD lockout module I will explain how to fix the fried module.

To do this you will need:

Basic electronics knowledge
A soldering iron (30 watt is plenty)
2 NTE289 transistors or equivalent
De soldering braid
small wire cutters (nail clippers worked for me)

I am not going to go into great detail of how to do this since i assume anyone doing it will have some general electronics knowledge. I will post the steps to do it though.

#1 remove the board from the module by unsnapping the back & sliding it out.
#2 identify the lead positions
#3 using the desoldering braid & iron. Remove the solder from the leads & remove the old transistors.
#4 Identify leads on new transistors & solder them in place.
#5 Clip extra wire off the leads
#6 Reinsert the board into the case
#7 Reinstall the module & test drive truck.
#8 Congratulate yourself on your success

This repair costed me a total of $6.18 (1.39 each for transistors, 2.99 for desoldering braid & .41 to the crooks in the capitol)

 

Very interesting find. Nice work

 

You're welcome.
I hope this helps someone else fix thiers

BTW. . . do any other years use this setup, or is it just a 91.5 thing??

 

Yep. Ain't having an orphan fun?

 

I have the same problems that you were having (no OD or back up lamps). However, my speedometer/odometer is not working as well. Were you missing the speedo as well or just no back-up/OD?

 

My speedo was working fine, but the backup lamp fuse was blown.

 

This is what I got - I show full voltage testing the engine, firewall and dash grounds.

Any thing I'm missing ?

 

Check your TPS and Crank sensor. There is plenty of info on this site in regards to those problems.

 

Hi - TPS checks out good, and this 91.5 doesn't have a crank sensor.