20'01 WJ LR Tail Lamp problem

2001 WJ Limited (automatic headlight control)

LR tail lamp operates normally (back-up in reverse, normal running lights, turn signal and brake lamp) as long as the headlights are off.

With headlights on, the running lights, back-up and turn signals work as normal until the brake pedal is stepped on. Then, the running lights go off and the brake light doesn't illuminate.

Checked the 6 pins on the Brake Light Switch according to the FSM and it is OK.

Checked the LR Lamp contacts and bulbs, all are OK.

I'm thinking it could be the left Multi-Function Switch on the Steering Column or a ground problem. I looked up the diagnostic procedure on this one but haven't run the procedure yet.

Any advice or way of further diagnosing the problem?

reboot

Reply to
reboot
Loading thread data ...

You are describing a faulty ground. The brake lights are getting ground through the running lamp circuit.

On the 93 I had to check the rear connector (behind the D pillar plastic) more than once. Eventually noticed one of the pins had nearly corroded away.

Might have to check the wiring harness at the lights and inside the body where it connects again.

Looking at the schematic, the brake switch provides 12V to the rear lamp. The park lights provide either ground or 12V (12V when the park lamps are on)

shield color/stripe color

Brake >---white/tan------> pin3 BULB pin5 Ground Park >---black/yellow---> pin6

Dang that schematic is giving me a headache.

Does it work with just the parking lamps on? I guess not.

I suspect a broken ground at one of the rear lamps or somewhere in the harness going back there.

formatting link
harness isn't going to be in the same place as mine. From what I can figure out the park lamp relay provides a ground back to the brake/parklamp bulb. this is where your brake light is getting ground when the parking lamps are off. That means that the ground from that bulb is broken somewhere.

Before digging into any of this I suggest checking the bulbs to make sure the sockets haven't metlted or the contacts eroded. I had that problem before.

formatting link

Reply to
DougW

formatting link
Your harness isn't going to be in the same place as mine.>

thanks Doug -

checked Bulbs - OK Bulb Sockets - OK visually, no signs of corrosion or broken wires

I've got the back interior side panel off now ... I don't see anything obvious visually - no breaks or pinches or abraded black tape.

what things should I be look for?

Matt

Reply to
reboot

Look for any connectors. Sometimes the pins inside will corrode or not be properly crimped. Also check the ground point by the seats. (it's sort of shown in the service book)

If you have a multimeter, check the ground wire back from the tail lamps. Should just be a plain black wire.

Reply to
DougW

formatting link
Your harness isn't going to be in the same place as mine.>

*********************** I've been reading the FSM a lot today and trying to use a logical process of elimination ... but I have to admit that electrical bits and magic smoke aren't my strong suit.

When I look at the Ground Distribution Diagram 8W-15-13 I see a body ground at G301 located beneath the driver's seat

This ground circuit grounds also grounds the Auto Day/Night Mirror and Fuel Pump. Since both of those work, I conclude that the Body Ground and Splice 307 are OK.

So it has got to be one of the following:

- a break in the black wire between the connector at the rear lamp and Splice 307 (not likely because there is no chafing on the tape and the truck hasn't been in any kind of accident). or - a bad terminal (#5) on the end of the harness or - a break in the electrical traces within the lamp housing or - a bad lamp socket (it has a slight brownish color like it has gotten warm) or - a bad lamp (it's new)

Is my logic flawed? Any different suggestions?

Matt

Reply to
reboot

If you don't have a multimeter, this would be a great time to get one. You can find the problem quickly with a wiring diagram and a meter, while without it, the job will be largely guesswork and replacing things unnecessarily.

As another poster said, *almost* certainly a bad ground.

Reply to
St. John Smythe

Valid assumption.

I agree. The only way to know for sure is to ohm it out.

That could cause it. Have you checked to see if pin5 is properly grounded?

Could be. My rear lamps use sockets and wires, a bad trace or melted solder joint could definatly cause problems. That's where I usually take the unit out and check every trace and connector with a DMM.

Classic example from my VIC (Vehicle Information Center)

formatting link
trace (telltale brown lacquer)
formatting link

most sockets do get that brownish look. You have to look real close. The older spring types like mine would melt just enough for the spring to not provide enough contact.

Don't think a bad lamp would cause that problem.

Your logic is spot on. Finding the fault is an exercise in eliminating every path till you find the one that has problems. Just be aware that sometimes things will check out, especially if the connection is loose. Those are always the biggest pain.

I always suspect connectors, those seem to have the greatest chance of going bad over time. Especially those exposed to any humidity or road salt.

Reply to
DougW

u have to buy a whole new rear tail lamp....here is a simple test, take the other sides unit off and hook it to the bad side... it should work just fine....look on line for a good cheap deal or a junk yard... here is the problem, the heat of the lamps melt the lamp modules electrical and jeep does not sell that part as a single unit...yes you can unscrew that electrical part but as I said. no one sells that simple piece....I have replaced both back whole rear tail lights ... about 60 dollars ... good luck

Reply to
Mindy

Buy a keyboard with a caps key and at least the letter "y" and then stop top posting.

Reply to
Joeseph P. Blow

*********************

I tried this and it worked ! So now I've isolated the problem to the lamp housing and it's electrical circuit. When I plug the driver's side lamp housing into the passenger side wire harness, the problem follows the lamp housing.

Funny thing - I used my (circa 1979 Radio Shack analog) multi-meter and confirmed continuity between the socket contact pads and the pins at the connector and everything checked out OK. When I get the replacement lamp housing I'll tear this one down to see what the problem really is.

Thanks for the suggestion Mindy.

Thanks for the advice DougW

Matt aka reboot

Reply to
reboot

Glad you figured it out. If you get a chance take some pictures of the housing. It could be as simple as a slightly deformed connector that isn't making contact with the bulb.

Reply to
DougW

formatting link
>Your harness isn't going to be in the same place as mine.>>

I wouldn't say flawed. More like totally missing.

The LOGICAL thing to do is verify what you have/don't have at the lamp housing connector with a test light or volt meter BEFORE pulling panels and wringing your hands over possible wiring/splice/body ground problems.

At this point, you still haven't even done any testing to find out if it's a problem on the car side or the lamp side. You have the FSM and have looked up the test procedure. What are you waiting for?

Reply to
bllsht

why dont you just shut the f up you doush bag your just another troll as far as im concerned and your not welcome here

Joeseph P. Blow wrote:

Reply to
Jeep America #1

well you fraud i hope your proud of yourself you got plonked because your a smart ass and not helping somebody out

just like the trolls in this group like 24butt punk fraud cujoke desuckpoppet and williams nemasis the worst troll of all who dosent even care

bllsht wrote:

formatting link
>>Your harness isn't going to be in the same place as mine.>>>

Reply to
Jeep America #1

Wow. Do you still suck your mom's dick with that mouth?

Reply to
Joeseph P. Blow

like I said, I have replaced 2 housings....even the warranty will not cover this because this is cosmetic as in broken outer light fixture even though it is the internal electrical ... this is what this group is good for, helping and sharing at times our own problems and solutions....if u can solve the mystery of the circuit and find a solution, please post .... it will save many money in not having to buy the whole housing....

Reply to
Mindy

Who put you in charge Billboi? Has no one told you there is a new President now.

Will

Reply to
Williams Nemesis

LOL

Hey, you're the one who asked if your logic was flawed. If you don't wanna know, don't ask. Either you don't care to learn anything or you're not smart enough to recognize solid information when you see it.

Reply to
bllsht

Grow up little boy.

Reply to
bllsht

Gee Billie you think he's a fraud? Looked in a mirror lately?

Mirror again! And you've helped whom?

mirror again, you really should stop blaming other people for your own inadequacies.

Yeah, whats it like to have no friends Billie?

Reply to
Williams Nemesis

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.