How to fix brake switch (not replace)

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treehan77

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Today my cruise control stopped working. A quick check showed no brake lights either. No dash warning lights will come on. Pulled several codes related to cruise switch, brake lights etc.

P1574 Stoplamp switch circuit
P0568 cruise control set switch circuit
P0567 cruise control resume switch circuit
P0741 Torque converter clutch Tcc system stick off (?!)

I believe You will need to clear these codes before it will work again. Mine came back after a drive, so here’s what to do about that.

In case you wondered, here's how to brake switch works on the GTM800 (my 2005 anyway): Essentially a plunger pushes down and opens 2 normally closed contacts, and closes 1 normally open contact. There is a plunger with a heavy spring inside the switch. Pressing the pedal pushes the plunger in. Mine had significant black electrical burns/tarnish at the contacts inside. Just needed cleaning and voila, cruise and brake lights work again.

You can pry the switch apart easily with a small screwdriver. Take a picture so you know how each of the 6 contacts fit. I took one out at a time and lightly sanded the black off the contacts themselves. Be careful, if the spring pops out, find it and squeezer it back in. After 15 minutes of looking for the spring, i took out all the contacts to put it with the plunger back in haha. Then i reinserted each contact. Otherwise, you will bend them. Pop the switch back together and reinstall. You can use a meter to test if you want. Two of the contacts will show continuity at rest. The last one, you will need to apply considerable force with a screwdriver and something and then it will shows continuity, and the first two will not.



Yes, you can replace this switch for $17 from the local auto big box place, and you might want to. Amazon has the OEM part for $17 also (I didn't want to buy a whatever brand, and didn't want to wait). (Putting the little clip back on is a PITA).

GM Genuine Parts D891A Brake Light Switch​


Here's some pictures for reference, and a link to a video that shows the removal/installation process of the switch itself.
 

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clandr1

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Interesting timing. Went to pick up dinner tonight and I noticed my brake lights weren’t working 100% of the time. I remembered seeing this thread a couple days ago, so came back to review the videos and photos.

I pulled the switch, cleaned the contacts, and had it reinstalled in about 20 minutes. The $11 OEM replacement is en route from Amazon, but with a Friday ETA so I figured I’d try to fix it for peace of mind for the next three days.

Thanks for posting this!

Edited to add: there are different part numbers for trucks with adjustable pedals versus non adjustable, so make sure you order the right part. I have adjustable pedals and my part number was D1583G.
 
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Doubeleive

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another thing that happens is the brake switch can get twisted slightly and won't make contact and therefore not work, the fix is to simply twist it back by hand a smidge
I don't know why gm does not make them so they will lock into a specific place but they don't.
 

clandr1

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Glad it got you up and running. I’m just gonna see how long mine works before ordering a new part. I’m guessing it works fine forever lol

You're probably right - I bet it will last you forever, but for how cheap the replacement part was I figured what the hell - might as well "splurge" since I haven't had a car payment in about 14 years LOL
 

Mark Elliott

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Today my cruise control stopped working. A quick check showed no brake lights either. No dash warning lights will come on. Pulled several codes related to cruise switch, brake lights etc.

P1574 Stoplamp switch circuit
P0568 cruise control set switch circuit
P0567 cruise control resume switch circuit
P0741 Torque converter clutch Tcc system stick off (?!)

I believe You will need to clear these codes before it will work again. Mine came back after a drive, so here’s what to do about that.

In case you wondered, here's how to brake switch works on the GTM800 (my 2005 anyway): Essentially a plunger pushes down and opens 2 normally closed contacts, and closes 1 normally open contact. There is a plunger with a heavy spring inside the switch. Pressing the pedal pushes the plunger in. Mine had significant black electrical burns/tarnish at the contacts inside. Just needed cleaning and voila, cruise and brake lights work again.

You can pry the switch apart easily with a small screwdriver. Take a picture so you know how each of the 6 contacts fit. I took one out at a time and lightly sanded the black off the contacts themselves. Be careful, if the spring pops out, find it and squeezer it back in. After 15 minutes of looking for the spring, i took out all the contacts to put it with the plunger back in haha. Then i reinserted each contact. Otherwise, you will bend them. Pop the switch back together and reinstall. You can use a meter to test if you want. Two of the contacts will show continuity at rest. The last one, you will need to apply considerable force with a screwdriver and something and then it will shows continuity, and the first two will not.



Yes, you can replace this switch for $17 from the local auto big box place, and you might want to. Amazon has the OEM part for $17 also (I didn't want to buy a whatever brand, and didn't want to wait). (Putting the little clip back on is a PITA).

GM Genuine Parts D891A Brake Light Switch​


Here's some pictures for reference, and a link to a video that shows the removal/installation process of the switch itself.
Thank you for this ,, you’ve described my issue almost to a T ,, on my 06 Yukon my top brake light still works but cruise and tail light brakes are not functional,, would you say I have the same issue ?
 

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