"Service Brakes Soon"

[Johnms]

2009 Yukon XL 1500 - I am getting a "Service Brakes Soon" message - but only when trailering. I have had my brakes served twice since this started and that includes a complete fluid replacement. I did have a sticking rear caliper replaced last year. The braking seems normal with no issues. Can someone tell me exactly what conditions trigger this warning?

 

[OR VietVet]

You have a problem with the trailer brake wiring, IMO.

 

[Fless]

Read that code with a scanner that will do more than powertrain codes, like a Tech 2. Might help point you in the right direction.

 

[Doubeleive]

SERVICE BRAKE LIGHT/WARNING, WITH NO ABS LIGHT
1. low brake fluid or brake fluid sensor is bad or going bad
2. stuck proportioning valve
THERE IS REALLY NO OTHER CAUSE WHEN THERE IS NO ABS LIGHT ON

unplug brake fluid sensor, if the warning goes away then most likely just a bad sensor, if brake work was very recent then prop valve could still be stuck but they usually unstick themselves after a bit or try hard braking several times on a rock/unpaved road

IF THIS WAS A 2021+ then it could be other things since GM decided to add sensors on the brake pads.
ALSO SERVICE TRAILER BRAKE IS A DIFFERENT SYSTEM

***could be when you hook up the trailer it changes the angle of the vehicle and therefore brake fluid and it throws the warning
if the brake fluid is found to be low, check all 4 corners for a leaking caliper

 

[Foggy]

I have gotten that message before when trailering...
Check your trailer bulbs and if any aren't working..
Check your plug from the trailer to the Truck.. Thats what mine was.
The plug was just being 'moody'

 

[Johnms]

Here is a follow-up - Just got the call from the mechanic. The brake booster was failing, they are replacing the brake booster and the sensor switch.

 

[Doubeleive]

Here is a follow-up - Just got the call from the mechanic. The brake booster was failing, they are replacing the brake booster and the sensor switch.

that's odd, was it leaking? or where you having any other braking issue's?

 

[Johnms]

I was surprised too and I do not know how they tested the booster to arrive at that issue resolution. Since it only came on (briefly but a couple of times and whenever I trailer) I suspect that the extra weight of the RV on the booster (if it was having issues) would be when the light would come on. However, it seemed to break fine every time.

 

[Doubeleive]

I have gotten that message before when trailering...
Check your trailer bulbs and if any aren't working..
Check your plug from the trailer to the Truck.. Thats what mine was.
The plug was just being 'moody'

can you confirm that was service brakes or service trailer brake?

 

[Johnms]

can you confirm that was service brakes or service trailer brake?

It was the Yukon's brakes system. The trailer has electric drum brakes without any other components.

Doubeleive​

Wes​

Supporting Member
JoinedNov 7, 2017Posts18,905Reaction score25,097LocationStockton, Ca.

I have gotten that message before when trailering...
Check your trailer bulbs and if any aren't working..
Check your plug from the trailer to the Truck.. Thats what mine was.
The plug was just being 'moody'

can you confirm that was service brakes or service trailer brake?