Jeep Grand Cherokee WJ Reverse Light Hack

Introduction: Jeep Grand Cherokee WJ Reverse Light Hack

The reverse lights are a known problem on this generation of Jeep Grand Cherokee. 99-2003. The factory switch that activates the reverse lights is part of the valve body inside the transmission. When it fails typically the only problem is the lights not working, so I was not about to pay the $400+ for the valve body and open up the tranny.

Here is what I did to get the lights working and pass my state's inspection.

Step 1: Locate the Trailer Wiring Harness

It is located in the drivers side rear most cargo panel. This is where I got power from and also where I tied into the back up light circuit.

Step 2: Use a 12 Volt Relay to Make Connections

I used a Bosch 5 pin 12 volt relay

this wire bundle is a great place to tap into becasue it as all that you need to compete the job.

There is a constant 12v, Tap into that source and connect Pin 87 and 86 (86 would normally be switch input, we are going to use ground as the trigger) I used 3m Scotchloc to attach to factory wires.

Tap in to reverse line and connect to Pin 30

Now connect a wire (black is typical for automotive ground) to pin 85 This is what will run to the new switch.

Use a self tapping screw to attache the relay.

Step 3: Run Wire to Center Console

Route the new black wire installed up to the center console it under carpet or along the doors under plastic moulding. Sorry I did not take a pic of this step

Step 4: Remove Center Console is a great source for info on how to do this step.

Step 5: Make Bracket for Micro Switch

I used some scrap 1" flat bar (1/8" Thick) bent in to a stair. Then two self taping screws to hold it the body.

Step 6: Attach Mirco Switch

I used two tack nails to go though the switch body and into two holes I drilled in to the bracket. The nails act as pins and then I hot glued it together.

Step 7: Make Trigger for Switch

I used Plastic epoxy putty for this, It was used is to fill the gap between the micro switch and the shiftier, also it provides a small enough contact point (shaped like a triangle) so the switch is only activated when in reverse.

Step 8: Connect Wires to Switch

I soldered the wire on to the contacts of the switch, one is the wire we just ran from the relay and the other goes to ground. There is a bolt in the bracket for the parking brake handle that I used to attach a ring terminal to.

Step 9: Test Switch

Run the shiftier through the gears. Make sure that the switch does not bind the shiftier any any point. Then confirm that the switch is only activating when the shiftier is in the reverse position. You should be able to make small adjustments buy bending the bracket carefully.

Step 10: You Are DONE!

After testing put back any trim removed and reinstall the center console.

Grab a cold one and admire your work!

1 Person Made This Project!


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Question 1 year ago on Step 2

Hello, I was happy to see this hack as I have already replaced the TRS solenoid pack once and am unfortunately coming up for inspection and DO NOT want to do it again. I have done a lot of recent wiring work because of failed voltage regulator in the PCM, window switch gone bad, etc and I find the Jeep wiring diagrams difficult to follow though I have managed to figure things out. My question is in regard to your tap in the hatchback area specifically when you said,
"There is a constant 12v, Tap into that source and connect Pin 87 and 86 (86 would normally be switch input."
1. When you say connect Pin 87 and 86 what do you mean?
2. I attached a snip of one of your images. what is the black piece (circled in blue)? Something that the relay plugs into? is it prewired?



Answer 1 year ago

Sorry for the delay, i don't use this platform much anymore.
1. all "bosch style" relays have the same pin arrangement, i attached a pic. Its is how to identify which pins to use.
2. Yes its a premade pig tall for the relay, I almost always use them, but you can just use female spade connectors if you prefer.
i have had good luck with the ones linked above.

Hopefully this was not too late to be helpful.


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Question 2 years ago

What color wire is the 12V constant? Also is the reverse light the Violet/Black?


Answer 2 years ago

Sorry, This was several years ago and i did not note colors. I just used a test light to idenify what wire to tap to.


Reply 2 years ago

Worked well. Glad I didn't have to pull the transmission apart. I
currently just have a rocker switch near my radio to control the reverse
lights but if i have to get it inspected at some point I will use the
roller switch method. The red/white wire was the 12V constant and the
violet/black is the reverse light wire. I also finally added in my
reverse camera now that my reverse lights can trigger the camera.


Reply 2 years ago

Ha its alright. I will pick one up. Thanks!


5 years ago

Thanks for sharing :)