Tahoe Brake Booster

[tpwalsh]

Hello. I have a 2008 Chevy Tahoe with 145k miles. I've owned it for the past 6 years and have put half of the miles on the vehicle. I've had it serviced regularly and have had no major issues to speak of regarding the brakes. Last week I drove to the store and on the way back I noticed that the vehicle seemed to be slower than normal. After driving another block it became evident that all of my brakes were beginning to lock up. I eventually made it home and was able to disengage the brakes in the driveway by removing the brake booster vacuum line. I began the process of removing the brake booster with plans to quickly install a new booster. The trouble is that I cannot find a brake booster with the electric harness ports anywhere. Rockauto, autozone, advance, none of them have the part. They have boosters without the electric connections, but I want to install a new part that meets factory specs. Has anyone else experienced a similar issue? Any thoughts on why this particular part is so hard to get? Suggestions? Thanks you.

 

[Joseph Garcia]

There is a check valve within the brake booster assembly. Have you checked that for proper operation?

There are other areas not directly connected to the brake booster itself, that can cause the brakes to lock up, such as the ABS system.

Do you have, or have access to, a quality bi-directional scanner? If not, I recommend that you get yourself a quality bi-directional scanner to add to your tool box. Then, you will be able to read ALL trouble codes, along with a brief explanation/pointer to the source of your issue. You can test many of the truck's electronic functions with the scanner, in order to determine the source of an issue. You will also be able to reset/delete trouble codes, after taking corrective action. You will literally save thousands of dollars in diagnostic and repair costs over the life of your truck, and you will most likely recoup the cost of the scanner within 1 year.

Another option is for you to post the last 8 digits of your VIN, and @915_Tahoe can check into the specific brake booster that you have and potential availability.

Last, if all other options fail, you can check out a local salvage yard or see if there is a nationwide salvage parts availability catalog.

 

[tpwalsh]

There is a check valve within the brake booster assembly. Have you checked that for proper operation?

There are other areas not directly connected to the brake booster itself, that can cause the brakes to lock up, such as the ABS system.

Do you have, or have access to, a quality bi-directional scanner? If not, I recommend that you get yourself a quality bi-directional scanner to add to your tool box. Then, you will be able to read ALL trouble codes, along with a brief explanation/pointer to the source of your issue. You can test many of the truck's electronic functions with the scanner, in order to determine the source of an issue. You will also be able to reset/delete trouble codes, after taking corrective action. You will literally save thousands of dollars in diagnostic and repair costs over the life of your truck, and you will most likely recoup the cost of the scanner within 1 year.

Another option is for you to post the last 8 digits of your VIN, and @915_Tahoe can check into the specific brake booster that you have and potential availability.

Last, if all other options fail, you can check out a local salvage yard or see if there is a nationwide salvage parts availability catalog.

Hi Joseph, I used an obd2 scanner, not a bidirectional scanner. It did not pick up trouble codes. Thank you for the recommendation. I guess I I correctly assumed that disconnecting the vacuum line from the brake booster resulting in the brakes releasing indicates there was a problem with the booster itself. I'll try to investigate how to test the check valve in the brake booster. Thanks again for your help

 

[Joseph Garcia]

Hi Joseph, I used an obd2 scanner, not a bidirectional scanner. It did not pick up trouble codes. Thank you for the recommendation. I guess I I correctly assumed that disconnecting the vacuum line from the brake booster resulting in the brakes releasing indicates there was a problem with the booster itself. I'll try to investigate how to test the check valve in the brake booster. Thanks again for your help

Glad to assist. And, if it is related to the check valve, they are cheap to replace.

Just keep in mind that simple scanners (not-bidirectional) typically can access only top level codes, but they cannot read sub-system codes, where the most important data for troubleshooting reside.

 

[Fless]

How about posting a pic of this booster that has the electrical connector, and showing the connector?

 

[tpwalsh]

Glad to assist. And, if it is related to the check valve, they are cheap to replace.

Just keep in mind that simple scanners (not-bidirectional) typically can access only top level codes, but they cannot read sub-system codes, where the most important data for troubleshooting reside.

Installed the new brake booster last night. Thought everything seemed ok. Drove 20 miles to work this morning without issue. Tried to leave work this afternoon and could not move the truck. All wheels locked up again. Tried removing the vacuum line to release pressure, brakes remained locked. Put a scanner on it and found 4 codes, C0131, C0299, C0561, and O0073. It's becoming evident that the issue may be a failing ABS module, especially with the C0131 code. Thoughts?

 

[Joseph Garcia]

@Doubeleive ; @swathdiver

 

[Doubeleive]

need more troubleshooting to verify things, i doubt the brake module (ebcm) is the issue and is instead being affected by the irrational brake pressure

**when you installed the new booster did you swap any old parts over?

Also the 00073 is a faulty ambient air temp sensor you will want to check that or just replace the sensor it can lead to other issues but is likely unrelated to the brake problem
it is mounted to the front of the radiator support behind the front grill

1. Code Breakdown​

• C0131: ABS Brake Pressure Sensor Circuit This is the "root" code. The EBCM (Electronic Brake Control Module) is detecting an irrational signal from the sensor that measures how hard you are pressing the brake pedal.
• C0299: Brake Booster Performance The computer detects that the brake booster is not maintaining the correct vacuum or pressure. This often triggers "Service Brake Assist" on your dashboard.
• C0561: System Disabled Information Stored (Invalid Data)This is a "sympathy" code. Because the ABS module is confused by the brake pressure (C0131), it tells the Traction Control and StabiliTrak systems to shut down for safety. Fixing the brake issue will make this code disappear.

2. Most Likely Causes (In Order)​

A. Faulty (power Brake booster Pressure Sensor (Most Common)​

On many GM vehicles, this sensor is built into or attached to the master cylinder. If it fails, it sends a "spike" in pressure data that the computer knows is impossible, triggering the C0131.

B. Failing Brake Booster or Vacuum Leak​

If your brake pedal feels "hard" or you hear a hissing sound under the dash when you press the brakes, the booster is likely leaking. Code C0299 specifically monitors the booster's ability to help you brake.

C. Brake Pedal Position (BPP) Sensor​

A miscalibrated or failing sensor at the top of the brake pedal arm can cause the system to think the brakes are being applied when they aren't, or vice versa.

3. Recommended Troubleshooting Steps​

1. Check Brake Fluid Level: Ensure the reservoir is full. Low fluid can occasionally cause pressure fluctuations.
2. Inspect Vacuum Lines: Look at the thick rubber hose going to the large round Brake Booster behind the master cylinder. If it is cracked or hissing, replace it.
3. Scan Tool Data: If you have access to a high-end scan tool, look at the "Brake Pressure Sensor" data stream.
   • With the pedal up, it should be near 0 PSI.
   • If it shows a high number (like 2000 PSI) while your foot is off the pedal, the sensor is bad.

Summary​

In 80% of cases with this specific trio of codes, the fix is replacing the Brake Pressure Sensor or the Brake Master Cylinder Assembly. If the pedal feels physically harder to push than usual, replace the Brake Booster

 

[Doubeleive]

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[tpwalsh]

need more troubleshooting to verify things, i doubt the brake module (ebcm) is the issue and is instead being affected by the irrational brake pressure

**when you installed the new booster did you swap any old parts over?

Also the 00073 is a faulty ambient air temp sensor you will want to check that or just replace the sensor it can lead to other issues but is likely unrelated to the brake problem
it is mounted to the front of the radiator support behind the front grill

1. Code Breakdown​

• C0131: ABS Brake Pressure Sensor Circuit This is the "root" code. The EBCM (Electronic Brake Control Module) is detecting an irrational signal from the sensor that measures how hard you are pressing the brake pedal.
• C0299: Brake Booster Performance The computer detects that the brake booster is not maintaining the correct vacuum or pressure. This often triggers "Service Brake Assist" on your dashboard.
• C0561: System Disabled Information Stored (Invalid Data)This is a "sympathy" code. Because the ABS module is confused by the brake pressure (C0131), it tells the Traction Control and StabiliTrak systems to shut down for safety. Fixing the brake issue will make this code disappear.

2. Most Likely Causes (In Order)​

A. Faulty (power Brake booster Pressure Sensor (Most Common)​

On many GM vehicles, this sensor is built into or attached to the master cylinder. If it fails, it sends a "spike" in pressure data that the computer knows is impossible, triggering the C0131.

B. Failing Brake Booster or Vacuum Leak​

If your brake pedal feels "hard" or you hear a hissing sound under the dash when you press the brakes, the booster is likely leaking. Code C0299 specifically monitors the booster's ability to help you brake.

C. Brake Pedal Position (BPP) Sensor​

A miscalibrated or failing sensor at the top of the brake pedal arm can cause the system to think the brakes are being applied when they aren't, or vice versa.

3. Recommended Troubleshooting Steps​

1. Check Brake Fluid Level: Ensure the reservoir is full. Low fluid can occasionally cause pressure fluctuations.
2. Inspect Vacuum Lines: Look at the thick rubber hose going to the large round Brake Booster behind the master cylinder. If it is cracked or hissing, replace it.
3. Scan Tool Data:If you have access to a high-end scan tool, look at the "Brake Pressure Sensor" data stream.
   • With the pedal up, it should be near 0 PSI.
   • If it shows a high number (like 2000 PSI) while your foot is off the pedal, the sensor is bad.

Summary​

In 80% of cases with this specific trio of codes, the fix is replacing the Brake Pressure Sensor or the Brake Master Cylinder Assembly. If the pedal feels physically harder to push than usual, replace the Brake Booster

Wow what a treasure of information! Thank you for taking the time to read through my info and provide such detailed feedback. I will check into the brake pressure sensor and the master cylinder. I did have the master cylinder replaced in 2021. Also, to answer your question, yes I did switch over the Bosch power booster sensor that was on the original brake booster, so there is a possibility that the sensor is bad.

 

[Joseph Garcia]

Wow what a treasure of information! Thank you for taking the time to read through my info and provide such detailed feedback. I will check into the brake pressure sensor and the master cylinder. I did have the master cylinder replaced in 2021. Also, to answer your question, yes I did switch over the Bosch power booster sensor that was on the original brake booster, so there is a possibility that the sensor is bad.

@Doubeleive ,Wes, is THE MAN!!

 

[Doubeleive]

Wow what a treasure of information! Thank you for taking the time to read through my info and provide such detailed feedback. I will check into the brake pressure sensor and the master cylinder. I did have the master cylinder replaced in 2021. Also, to answer your question, yes I did switch over the Bosch power booster sensor that was on the original brake booster, so there is a possibility that the sensor is bad.

that sensor I think it your primary issue and may have been the original problem

also check or replace that ambient temp sensor it affects how the engine runs, idles, gas mileage, etc

 

[Doubeleive]

for instance if it is 40deg out and that thing is saying 70deg it's a problem or vica-versa, if it says it is 0deg when it is 40deg

 

[swathdiver]

What brand of parts are you using?

 

[tpwalsh]

What brand of parts are you using?

that sensor I think it your primary issue and may have been the original problem

also check or replace that ambient temp sensor it affects how the engine runs, idles, gas mileage, etc

Thank you Wes. Just wanted to follow up. The new brake Booster is a Reweaver from advance auto. Not exactly the brand I was looking for, but literally one of the only replacements I could find that had the sensor ports. Also I should mention a few other things that have happened since the brakes locked up on Sunday. I did try to begin bleeding the brakes, and as expected the first one I tried, rear driver caliper, the bleeder was seized. I did remove the caliper to try and get better leverage on a vice, no luck. I also shortened the push rod in the brake booster. I ended up having to move the vehicle before my new calipers arrived, so I had to put the original caliper back on, of course unable to bleed the line because the bleeder was still seized. I started the truck and was expecting the truck to have soft brakes due to air in the rear caliper line. However, to my surprise, the brakes felt almost perfect. I was able to drive it 20 miles without issue to my mechanic where it currently awaits a proper diagnosis and repair. I will post an update once I receive the findings. Thanks again everyone.

 

[Tahoe14]

RockAuto is another source for parts that members use and there is a discount code you can use.