2016 Yukon downshifting and sluggish at 60mph

[fixmyride]

it's my first post here. I hope i will get solution to my issue.

I have a 2016 Yukon at my workshop for Brake Cylinder replacement. After replacing the Brake cylinder car is not driving normal. First, It's Adaptive Cruise control says it's not available.
Second, car doesn't drive at more than 60km. It downshifts itself and revs up.

Worst part is It's not giving any DTC.

Please help me.

 

[Fless]

Welcome to TYF. Post up an introduction in the Introduction section, and include some pics of your rig.

By "brake cylinder" do you mean the master cylinder?

 

[Rygrego]

Sounds like your antilock brake system needs to be purged. You will need a bi-directional scan tool with antilock purge capabilities.

 

[fixmyride]

Welcome to TYF. Post up an introduction in the Introduction section, and include some pics of your rig.

By "brake cylinder" do you mean the master cylinder?

Sorry I wasn't clear enough. We changed Brake Booster and Master Cylinder

 

[sealandsky]

it's my first post here. I hope i will get solution to my issue.

I have a 2016 Yukon at my workshop for Brake Cylinder replacement. After replacing the Brake cylinder car is not driving normal. First, It's Adaptive Cruise control says it's not available.
Second, car doesn't drive at more than 60km. It downshifts itself and revs up.

Worst part is It's not giving any DTC.

Please help me.

Your engine is in "limp home mode". First thing to do is to disconnect your negative battery cable, clean the connection and reinstall. What the hell - Do the positive one while you are at it. If that does not remedy the problem, then it's time to go to your dealer...

 

[the highlander]

i wonder if this is an imported vehicle and you have passerby restrictions enabled.

 

[Doubeleive]

i wonder if this is an imported vehicle and you have passerby restrictions enabled.

 

[Doubeleive]

if the battery disconnect does not correct the issue then you need to go in there with a mdi and see whats up, the adaptive is offline for a reason if it was previously working and all you did was the master and didn't accidentally disconnect something or make the adaptive sensor go out of calibration then it would likely be brake related. It could also be why it is not allowing acceleration. If you poke around with the MDI and check all the system status you should be able to see it.

 

[B-train]

Some ideas here:

1) air in the system and needs to be bled like RYGREGO stated. Is the pedal mushy? Does it go low to the floor? Is it overly firm?
2) adjustment of pushrod? Does the master cylinder go to the "home " position and allow for the brake pedal rod to have a little bit of freeplay? Are any brakes dragging after a test drive? What are rotor Temps?
3) you have a vacuum leak possibly. Are all the hoses hooked back up? Are the electrical connections good at brake booster? Does the vacuum pump operate correctly (there is a bulletin about weak performance and might be covered by GM. --- this usually comes across as a vehicle that doesn't want to stop at low speeds ie: parking maneuvers)