1999 (1998 model year) suburban brake lights stay on when vehicle is off

[allletters]

Hi, first post so i hope this in the right place. Just bought a '99 suburban, it is a 98 model year, and the brake lights didn't work. I replaced the switch and now the brake lights stay on all the time, except when the vehicle is running then they seem to work normally. The pedal stiffens up after shutting the engine off and i am wondering if there is some sort of adjustment to be made there. I did put a known working switch from my '97 tahoe in to verify it wasn't a bad new switch and did not fix the problem. Any help is appreciated

 

[Erik the Awful]

Check your ground at the left rear of the vehicle. My son's truck (in my signature) had issues with the parking lights staying on and then not working when the ignition is on. We fixed that ground and everything works.

 

[RichLo]

Its normal for the brakes to stiffen up after you turn off the engine. The Vacuum brake booster isnt getting vacuum from the engine anymore.

And I think the newer ones keep the brake lights active after you turn the truck off to let people know your still braking in case something happened on accident. But they should obviously go off when you let up off the pedal.

 

[allletters]

Check your ground at the left rear of the vehicle. My son's truck (in my signature) had issues with the parking lights staying on and then not working when the ignition is on. We fixed that ground and everything works.

Thanks I will check the ground tonight but i don't think that would be the issue if the lights go out and function normally when i start the engine and press the pedal once. Never know though grounds can be funny

 

[allletters]

I should mention as well there doesn't appear to be any free travel in the pedal when the car is off, my tahoe you can depress the pedal about an inch or inch and a quarter

 

[allletters]

Checked the only ground i could find back there, the one that connects to the filler neck. No change

 

[GoToGuy]

It's in the rear, an inner frame ring terminal. It's not a car.
All vehicles brake differently, all have different " feel". New to you , new vehicle adapting. Does it brake and stop normally?

 

[Road Trip]

Checked the only ground i could find back there, the one that connects to the filler neck. No change

The ground that is involved with the rear brake & tail lamps is named G401. The first attachment
shows the wiring diagram, and the second attachment shows the physical location.

When you get a chance locate and clean G401 and let's see if that doesn't change the behavior.
(A marginal ground in this location has caused much baffling electrical behavior on several different
GMT400 vehicles.)

And by all means let us know what you discover.

Best of luck --

 

[allletters]

The ground that is involved with the rear brake & tail lamps is named G401. The first attachment
shows the wiring diagram, and the second attachment shows the physical location.

When you get a chance locate and clean G401 and let's see if that doesn't change the behavior.
(A marginal ground in this location has caused much baffling electrical behavior on several different
GMT400 vehicles.)

And by all means let us know what you discover.

Best of luck --

Thank you for the diagram abd picture that really helps, i will get at it after work tommorow

 

[someotherguy]

Its normal for the brakes to stiffen up after you turn off the engine. The Vacuum brake booster isnt getting vacuum from the engine anymore.

And I think the newer ones keep the brake lights active after you turn the truck off to let people know your still braking in case something happened on accident. But they should obviously go off when you let up off the pedal.

Correct, the brake light circuit is always hot regardless of key position on these trucks.

OP, while the truck is off and the brake lights are on, if you lift the pedal by hand a little bit - do the lights go off?

I'm thinking bad booster or possibly even bent booster pushrod from someone jamming on the brakes super hard in a panic stop. When working properly, it doesn't take much travel for the switch to activate.

Richard