Question about 2000 Jeep Grand Cherokee

4 Answers

Rear brake light doesn't work when headlights on

When the headlights are not on - all brake lights function properly.. as soon as I turn on the headlights the Left brake light does not work. Have taken it to a jeep dealer and another shop and one told me they could find nothing wrong -- the dealership told me they fixed it but they didn't. Tried changing the fuse and it doesn't help.

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  • Anonymous Jan 29, 2009

    My brake light work when my headlights are off, but when my headlights are turned on-and I apply brake pedel-the brake lights don't work. All rear lights go off except my tail gate brake light

  • Mark daniel Abadi
    Mark daniel Abadi Apr 22, 2019

    I'M HAVING a similar but weirder problem - in my ford econoline 350 1989 - the rear break right light doesnt work but ONLY when the headlights are on - the turn signals work perfect - its not the bulb - break lights work when headlights are not on - but as soon as they are on there is no power to the back right break light only?? please help

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4 Answers

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If you take the tail light assembly off and take the bulb out, you'll see three metal contacts on the tail light assembly.  Pry them up slightly and slide a small, folded piece of aluminum foil underneath it.  
Replace the bulb and try to reproduce the problem.  I found this fix online and did it to both sides of my car.. no problems since

Posted on Sep 23, 2008


I own a 2000 Jeep Grand Cherokee and I too had the same problem on the left tail light/brake light. Thanks to this website, I've regained my sanity (and stopped changing light bulbs). Additionally, I was not going to pay for a part unless I absolutely had to, and I was able to repair the light with info from this website. In return, I thought I'd post how I did it.
1. Remove the tail light assembly. Most of you know how to remove the light assembly if you've changed bulbs, so I won't cover that.
2. disconnect the wiring harness by sliding the red locking clip to the side in order to press the side of the male connector and pull apart.
3. Once you've got the tail assembly away from the vehicle and on a bench, remove the light socket for the tail/brake light. You will see 3 silver contact points inside the black plastic ring. 2 are grouped together and there is one that is opposite of the 2. The one by itself is the ground; the other two are the contacts for the tail light and brake light. The problem lies with the ground connector. (BTW, I tested continuity with all lights and contacts including the turn signal and the reverse light to verify that the circuit board itself was good, and it was).
4. clean all contacts with a Q-Tip and some sort of contact cleaner - rubbing alcohol will work.
5. You should notice that the ground contact is depressed into the plastic and the plastic itself is slightly warped down. I was able to use a small pair of needle nose pliers that have a 45 degree angle to press up on the contact from underneath using the opposite lip of the hole as leverage (very carefully). Once it had moved up a bit, I was able to wedge a mini-flathead screwdriver in between the metal contact and the plastic to force the contact up even further (again, very carefully). Once it looked even with the rest, gently reinsert the connector and test.
Hope this helps...

Posted on Sep 24, 2008

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  • Audrey Sep 22, 2013

    Thank you so much for the posting about the contactors above (9/24/08). My son has a 2000 Jeep Grand Cherokee and it was doing the same thing. I read your post and figured I'd give it a shot. I had a little difficulty lifting the contactors out of the warped plastic ring, but eventually got it with a sharp paring knife. You are correct, you have to be very careful not to break the contactors, so I went slowly. I had to put a tiny piece of aluminum foil under the contactor to keep it from smushing back down into the warped plastic when the bulb was re-inserted. Anyway, the fix worked like a charm. Easy fix (and I'm a female:))

  • Crystal
    Crystal May 25, 2014

    OMG....I am SO happy I came across this post! I have a 2001 Jeep Grand Cherokee and have been having this same problem. Replaced all the bulbs and fuses and finally ended up taking it to the car repair shop. Nothing seemed to work. Read this post, and followed the directions step by step and "Ta Da" everything is working now! Thank you, thank you, thank you! From reading all these posts, it seems like this might be a problem prevalent among Jeep owners....I wonder if the manufacturers are aware of it?

  • James Deloney
    James Deloney Jun 17, 2015

    Work and help very well thanks

  • James Deloney
    James Deloney Jun 17, 2015

    It works thank God and it took about 15 min

  • Doug Walker
    Doug Walker Dec 31, 2018

    Just tried this and it worked great. Thank You!


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Check fuses.?
scan the PCM yet?, for DTC errors.
is the battery at full 12.6vdc rested,?
does engine run ok?,
car drive ok?
do the headlights have full brightness.? brakes off and key in pocket?

never take a working car to any shop they cant fix working cars. (can't fix working cars...)
(but they will take your cash. no lie)
so what does this mean, ?
(im not going to guess like others.. ok)
Left brake light "does not work"??? (huh)
not work, (dead or dim?)
so the other brake lamps glows. with brakes and HL on. ok?
but the left does what. exactly,
ever take of the lens and watch all elements to see what is happening? with actual elements?
do brakes or HL or parks on cause fuses to blow?

does the park lamp on, cause the brake element to glow?
is that it?// yes, then park is shorted to brakes.
but that short causes both brake elements to fail, this way....
or is the brake element dead (out), with parks on? and brakes depressed.?

i have the full schematics, need that? sure...
it's not like a 1993 at all. sorry.
first is rule 1, if car has brass base lamps, they do short. (even in 1957 they did)
so replace all3 brake lamps. (this gets parks too)
the HL on , is park, did you see if the brake lamp fails just on park selected? and not full on head lights, sure, it did....
it's really park lamps doing this, and are all park lamps glowing front ,rear and side of car? in PARK? see my answers are mostly questions, as im blind and cant do the tests carefully my self....see?

there are many park lamps on the left side,
did you look at all of them? even front parks and side marker parks?
the Design, 101:
the newer jeeps run a BCM to control relays for lamps."body control module (computer it is)

lets review this design
the park switch(1 or 2clicks) closes at hand
the BCM sees this pure digital signal and the BCM commands on the park relay ,it closes and sends park voltage to all park lamps. (all are in parallel (key fact 2)

the head lights do not go to the rear of car, and is not related. (only park feed) not arguing just making the path clear. park.
it's park. (aka, as tails wrongly many times.)

"now the tricky part the relay oddly grounds the park feed, when not in park or HL mode."
HL means head light.... jargon...
the brake switch is not BCM operated at all, (clue3)
it has JUST a brake switch hardwired to the brake rear elements. (x3)
and the 3rd center lamp, does it fail too? not stated.
all 3 are in parallel so if there is a short, all 3 fail as one. does it ? seems not....
did you do the tests in the dark? to see other symptoms,? dim glowing ,etc?
dead or stuck on. both. or one is dim.
see why?
if the lamp is bad, (inside) they can short anything in there. (ground ,brake and park is there)
that is why replacing the silly lamp is job 1.

if the park shorts to HL
and hl are off, the brake element is now grounded from the relay.(ground)
this is what is happening in your car.
the lamp is shorted. (my guess, but i use my meter to not guess)
why not replace the $1 bulb,
and not get china bulbs that love to short, (cheap junky bonding glue inside base shell)

the secret here is the park line is grounded on this car, in park off. (HL and parks off)
unlike most other cars made. (yes tricky)

see my drawing to prove that.

this is your jeep (usa spec)
the park feed is grounded in park off. (HL and PARK OFF) !
also look for tailer wiring hacks first. then prev. collision damage to all brake wires. on the rear. careful inspections, find most of this fast. inspect each of the 3, brake blub sockets for damage of any kind and for sure SHORTS, after 3 new lamps replaced. (L/R / and center)
did i nail this subject, good !
this is the park relay. and is shown OFF.
rear brake light doesn't work when headlights on - 1061203-qhnazd2zj0blugugkzxcoztt-5-0.jpg

now lets do the fails other guessed here wrong.
the problem with helpers doing anecdotal stories, is that this is your car, not theirs! and your failure. (there are many fail modes so.... lets do just your car, not mine, not others... and silly guessing.)
1: the park socket pin open (retracted or rusty)
only kills that park element, sorry! that is a fact. this will not effect brakes ever. (lamps good) same is true with retracted (or rusty)brake element, only that one brake element) fails.
if the lamp ground fails all lamps fail that socket.
if main ground g200 fails, all lamps on rear of car fail dead.

2: the park wire is grounded when off.(at relay)
so knowing that, you then you know if the brake wire is shorted to park left. (by any means)
the brake fuse blows. (a dead short, it must)
(electric facts) that is because all brake wires are in parallel, and if one shorts all brakes are shorted.
but if ground is rusty there. (omg a double failure) the fuse might not blow. and you get dim lamps. brakes only, HL and park is off. now.

3: if the park wire is shorted on the left side to ground(by any means) that means the park fuse blows. as you flip the HL lever 1 or 2 clicks on.
if park is crossed over to brakes, all elements glow, all park and all brake.
brake and park, with park switch on only,
that is a bunch of lamps.
3 brake at rear.
2 rear parks
4 sides of car park
2 front park.
11 elements glowing or fuse blows.?

if the brakes are turned on now,with same crossover, and not park ON.
then the brakes see a ground (park relay) and blow the brake fuse fast. G200 ground good. (assumed)
end factorial.... i can do more, and double fails.

i was thinking last night why does jeep ground the park feed, when not used. (at relay)
answer, (IMO)
this prevents park/brake crossvovers, from causing
all 11 elements to glow (parks on , brakes depressed)
(omg front/side parks too , brakes on.)

they want the brakes lamps to only glow, brakes on
never the vast parking lamp feed, going hot. wrongly. and to blow the fuse, telling you that there is a huge short in the brake feed.
that is my idea there. Kinda cool really.

this cars interior lamps all have BCM drivers
so is not effected. (isolated it is)
some GC cars, have aiming head lights and a motor.
and this motor is wired to PARK feed. one more fact. i cant comment on that .. dont have (not fun to diagnose that..)
and the park feed goes to that, and to all park lamps front rear and side.
if the park main feed fails, all parks die.
if the park feed grounds, all fail. they are in fact run off ONE park feed.

The same is true on brakes, they are all parallel
but is not connected to park at all, in any why.

i have the book to prove all that.

only double fails are tricky.

i found this in google

the full park path.

Posted on Jul 02, 2015

  • 3 more comments 
  • Anonymous Jul 02, 2015

    if the socket plastic is warped that means
    the socket is bad, there is no hacking this. replace any sockets seen to have permanent damage. life is too short for running cheap plastic melted sockets, yes, really.
    sure to get home, my answer is for real and lasting ! repairs.
    same with mom kitchen aluminum foil.

  • _-__-___-_
    _-__-___-_ Jul 03, 2015

    replace all 3 bulbs
    clean the socket pins
    make sure the socket pins work and retract with spring pressure.
    clean all rust off pins
    do not use aluminum foil to fix cars. that is goofy.
    cure all wiring damage, (for what ever reasons, collision or uhaul hack jobs....)
    look for heat damage, (warping)
    in most cases this cures all.
    and fuses blown.
    if its still bad ,tell all symptoms of all brakes and park lamps on car. not just one.

  • Anonymous Jul 03, 2015

    keep and open mind, double fails HAPPEN.

  • Anonymous Jul 03, 2015

    "head lights on; brake function normal" (parks)
    ok, so the left park element glows, ONLY?
    in this one left socket (lens off looking only at bulb left?)
    then you depress brake and all 3 rear brake elements glow.? L/R& center?
    if you turn off parks, then parks auto ground
    and if the 2 LEFT elements are shorted, then brake activate now,, blows the brake fuse.
    did it?

    making you think the brake light fails but all 3 do really (L/R/C), because the fuse did blow.
    with just parks on do brakes glow?
    yes,/no. that takes looking at elements not lenses. in many cases.
    look at the glowing tungsten elements.

    for sure new rear bulbs x3 is fast easy and cheap, to do. and might cure 1/2 of a double failure..... or worse.....

  • Anonymous Jul 04, 2015

    no, im not saying mine had the same problem
    in fact, if seen them all. so never say that, as that is anecdotal and wrong to say.
    what I say is do the tests , stop guessing.
    let the reality of your car tell you what is wrong.
    take a class in electrics, and learn that failures can be vast in nature, and 10x that on things the MOVE. (rust , collision, and vibration caused most this and can compound)


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Check bulb in rear ive seen carbon build up cause problems aslo check bulbs for crossed filliments just replace them all there cheap enough

Posted on Sep 20, 2008

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