Hello all,

I just ran into my first problem with my new (to me) 2008 Dodge Grand Caravan SXT. The High Mount Stop Light, commonly known as the third brake light or CHMSL, is not working. The owners manual has the following to say:
----------------
LIGHT BULBS — Exterior Bulb Number
Center High-Mounted Stop Light . . . LED (See Note 1)

Note 1: The Center High-Mounted Stop Light (CHMSL)
uses LED lights that are not serviceable separately. The
CHMSL must be replaced as an assembly, see your
authorized Dealer.

----------------

So I have a few questions.

1. Has anyone changed this assembly on their own?
2. Could something else be causing this light to fail?
3. How can I get at the assembly to do some testing?

I only had a few minutes tonight to diagnose the problem, and I didn't see an easy way to get to the assembly. An initial search of the internet was unhelpful and nobody seems to carry this part. Any help or insight would be greatly appreciated.

Thanks!
Jason

 

Welcome to DF
Here is some information right out of the dealers manual. Mounted Stop/Removal
REMOVAL

NOTE: The CHMSL illumination on this vehicle is accomplished by LED bulbs and these bulbs are not serviced separately. The CHMSL must be replaced as a unit.
1. Disconnect and isolate the battery negative cable.
2. Open the rear liftgate, and disconnect the washer hose from the CHMSL unit.
3. Remove the liftgate spoiler assembly.
4. Remove the two screws from the CHMSL unit and remove the unit from the liftgate spoiler assembly.

 

Thanks Master Tech,

You don't happen to have the instructions for removing the liftgate spoiler assembly do you? Or do you think it will be obvious when I look at it tomorrow?

Thanks again,
Jason

 

23 - Body / Exterior / SPOILER/Removal
REMOVAL
Labor Operations: Click to display a list of Labor Operations associated with this procedure




1. Open the rear liftgate.
2. Remove the two fasteners on each side of the liftgate.
3. Remove the upper trim panel on the rear lift gate.

NOTE: The two outboard clips are accessible through holes and can be compressed with a 8mm socket. The middle clip is blind and requires a 8mm box wrench. If the center clip is broken it is service part.
4. Remove the two fasteners and unclip the 3 pushpins for the rear spoiler.
5. Disconnect the electrical connector for the brake lamp.
6. Disconnect the washer hose from the spoiler.
7. Remove the spoiler from the vehicle.

 

So it looks like there might be a deeper issue here. Yesterday I was going to start tearing into the liftgate to test the light. My brother was over the house and I just wanted to double check that the light was still out. I jumped in the van and pressed the brake pedal and he reported zero brake light activity. I tried the emergency flashers and they worked. I started the engine and the two lower brake lights started working with the pedal, but still no 3rd brake light. Key off again, and back to no brake lights. This is quite odd. I've just started researching and I will check the fuses tonight. I wanted to know if anyone else has seen this problem.

Thanks!
J

 

I pulled fuse M1 from the TIPM when I got home after work today. It was blown. I replaced it with a matching 15 AMP fuse and third brake light is functional again, along with the new symptom of no brake lights with the Key Off.

It's funny because my normal thought process would have been check the bulb -> bulb ok? -> check the fuse. But with the LED module I got all sidetracked trying to take it out to test it. A reminder to myself to K.I.S.S.

Hopefully this will not reoccur.

Thanks for the help!
Jason

 

An update, in case anyone has a similar issue. This has been happening on and off since I first posted. Sometimes a fuse lasts a few days, sometimes it lasts a month. I am thinking about replacing the brake pedal switch when I get a chance. I will update this thread again at that time.

 

Well, I replaced the Brake switch over the weekend and installed a new fuse. The wife took the van on Tuesday and this morning it had blown the fuse again and had no CHMSL or brake lights when the key is off.

Does anyone have the wiring diagram for the brake lights? I had a copy but I lost it.

 

Try a 20 amp fuse? If it blows the 20 amps, your problem will be a wire is shorted somewhere. If 20 amp fuse works fine but not 15, that means one of ur light bulb is drawing more current than it suppose to.
This is the easiest thing to do without any diagnostic tools.

 

I'm really hesitant about putting a 20-amp fuse in there. From what I do remember from the wiring diagram is that this circuit flows through the BCM. It is very interesting that the fuse does not blow immediately, so it is probably not a dead short, but the fact that the side brake lights don't work until you turn on the key is perplexing.