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CHMSL and cruise control issues

Dluvr22

Dluvr22

PM 2014
PM 2013
Full Member
Joined
Jul 27, 2008
Messages
2,247
Location
Minneapolis, Minnesota
A couple of days ago I tried to use the cruise control while on my way home from work and it just wouldn't work.
Tried putting it on from the stalk on my 02 steering wheel and nothing.

After a couple of presses it finally came on and I was able to set a speed.
Just to test it I turned it off again and tried putting it on and lo and behold it would not come on.

This goes on for the rest of my drive home where it intermittently works when turned on.
From experience I know the first thing to check is my brake lights and brake switch so I get home pull into the garage and tried to used the glass in the garage door as a mirror to check.
There I notice that while the brake lights in the tail lamps come on, the CHMSL doesn't.
Now I am perplexed.
So first thing I do is turn the truck off and pull the CHMSL fuse under the hood and eyeball it and it is fine.
Since I have LED tail lights I figure the next thing to do is to check my resistor to make sure it is not the culprit for the cruise control issue.
I get out, found a brick and put it on the brake pedal and went to the back of the truck to check and this time the CHMSL is on.
Now I am thinking ok there's hope yet.
Maybe the fuse was just loose.
Go back to the driver side remove the brick so the brakes are not applied, and step on the pedal while watching the glass in the garage door and it doesn't come on again.
Put the brick back , walk to the back of the truck and still not CHMSL.

Am I missing something here?
I know there is a relationship between the brake lights and the cruise control where if there is a blown bulb and the cruise control circuit is not sensing the correctr resistance from the bulb it will not work.
How does the CHMSL fit into this circuit?
Should I be treating this as 2 separate issues rather than something related?

Also even though I do have LED tail lights, I still like the neon CHMSL my 02 came with so i am on the fence about getting a replacement without being sure my bulb is gone.

Your thoughts?

P.S. now that I am writing this I am thinking of other things I should have done like swapping the fuse with another to ensure the fuse is not faulty.

 
My previous vehicle was a 1999 Suburban.

I also had a problem with the cruise control that sounds a lot like yours.

The problem ended up being the brake light switch located above the brake pedal.

About a $20 part, if I remember correctly.

All of my brake lights, including the CHMSL worked normally.

What I found out was, there are two separate electrical contacts and circuits contained within the brake light switch.

The circuit and contacts that worked the brake lights worked just fine.

The circuit that worked with the cruise control was worn out and would make contact from time to time, but was getting worse.

I replaced the switch and everything worked great all the way to trade in several years later.

I'm not sure what the problem is with your CHMSL, but if it were me, I would replace that brake light switch first and maybe that will solve all of your problems.
 
So I have some bad news for you.  :cry:

The 02 neon CHMSL's all go bad eventually, either electrically or USUALLY because the neon slowly migrates out out over time. This is a well known issue and GM stopped making the neon units very early on due to the failure rates. Very disappointing because they have that really cool soft glow.

The LED type, such as used in later years, 03, 04, etc., are a direct replacement. (You can replace the LED unit only and not the entire ABS section it resides in.) I do not know the transition time, for example, I do not know if any 03's still came with the neons or not.

My 02 neon CHMSL got intermittent in 2010 (It  lasted a REALLY LONG time!) and then finally died. These things are not in any way repairable.

You might find an LED version cheap at a wrecking yard. I forgot what the new LED one cost me at the dealer.

:B:
 
my 03 has the neon ...
you might take out your taillights and check sockets for corrosion... my cruise was intermittent and it turned out one side was built up pretty bad (led lights) so i cleaned them put some electric grease on and put them back in no problem since  (y)
 
Just a FYI if the 3rd brake light is out no the Cruise Control will not work right.
When you first turn on the Cruise control it does check things like the 3rd brake light, your speed, your stored engine fault codes, if any has issues the system will not engage.

It does not check the normal brakelights only the 3rd brakelight. The 3rd brakelight is the only true brake light circuit you have the lower 2 are controlled by the BCM and Flasher module.

HTH
 
I have to say ditto to the switch on the break pedal. I think I got it from the dealer for 23$ In stock item.
 
I am under the impression that the brake switch is a common issue in our trucks and this is one of the symptoms. If it is not the brake switch you likely have a bad light. The deal with the brick though sounds like the switch is broken and only works intermittently. If the switch is a $23 part it would be much simpler to just replace it and find out than to even take it to the dealer and pay a half hour or hour for them to diagnose.
 
It could well be the switch causing the 3rd brake light. not to work.
 
As mentioned by EXT4ME these switches have 2 circuits in them. This is common in other GM vehicles as well and similar symptoms follow similar diagnostic paths. I believe one is to the lights and one to the system. I actually heard this first about my 1994 Caprice although I don't have cruise control in mine at the moment.

Rodney
 
Thanks guys .
Had a busy Friday and weekend.
Not driving the Avalanche much for the last couple of weeks as I get it ready for winter.
I'll look into that switch tonight then follow up with the CHMSL.


I've also checked the taillights.
No corrosion affecting the LED circuit there so that is one thing checked off.
 
Over the weekend I checked the fuses for the CHMSL and the cruise control and they were both OK
I also replaced the brake light switch on the brake pedal.
The end results is I have now resolved the cruise control issue as it now works.
Either the fuse was not making proper contact or the brake light switch was the culprit but I will not know as I did both together.
On the other hand the CHMSL still does not work so I just purchased a smoked LED version off eBay and will be installing it this weekend.
In the end I think I'll like the smoked LED better as it should blend in with painted cladding when off and light up with LEDs to match the smoked tail lights and LEDs in the sail panel screws.


 
Dang it. this CHMSL is driving me mad.
My LED version is in the mail and I just noticed that my neon ones are working today.  :beating: :beating: :beating:
Got me wondering if I'll see the same intermittent behavior with the LED version and need to start looking elsewhere for a fault.

Ugh I hate these electrical gremlins
 
next time it quits press the brake pedal and check voltage at the light  (y) that will at least let you know before the led one shows up
 
wyotonka said:
next time it quits press the brake pedal and check voltage at the light  (y) that will at least let you know before the led one shows up
Click to expand...

Unfortunately I have to take apart the cladding to do that.
GM did not make this one easy.


I'll check it again on my way home and when I do take it apart this weekend I'll test it multiple times before putting it back together.
 
yea... i havent gotten around to taking mine apart but i was thinking it would make your troubleshooting a little easier
 
You should look at where the wire goes and find an inside location to test the voltage and see what happens. You don't HAVE to pull the cladding off to see if it is working. Although going directly to the light may show that you don't have any issues between the wire where you would test it and the light. Chances are the wires travels down a channel under the carpeting inside the truck.
 
I hate to bring back life in a old thread but did you ever find the gremlin in your situation? I'm having the same issue with my 04 Z66. I also have led bulbs. I went last weekend and pulled a light off a 04 that way in the junkyard since mine was not working. I pulled everything off took out the bad light and connected the one from the boneyard and it worked. I went to check it today and it has also quit working.
 
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