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Discussion Starter #1
Gentlemen and lady's - I got a 2002 ext with a strange braking issues.....
Going back to the beginning -
A friend of mine originally purchased this truck ( knowing it had transmission issues ) when he purchased it everything ( brakes and engine related ) worked as it should.... As far as he remembers brakes work..... The truck got pushed to the side ( got tied up with life ) a few mths after being pushed to the side I came along and purchased the truck..... Sometime while the truck set - it lost the brakes - brakes go to floor......
This is not air in the lines.... I have done my fair share of brake repair -
Here is what I know for sure.....
The pedal goes almost to the floor - what little pressure it makes ( it holds ) ( does not bleed off )
There are no leaks I can see.
Vehicle has new master cylinder-
If you plug both ports for the master cylinder the pedal stays firm and strong.....(does not go to floor)
If you connect the rear line - the pedal stays firm.( Does not go to floor)....

Iv bleed front wheels -

When you connect the front line the pedal starts going to the floor again ( even with rear port plugged )

( The issue is something to do with front line? )maybe?


The front brakes appear to work properly ( they both get hot equally )


( The rear brakes do not get hot ) ( ice cold ) ( both rear wheels )

Any suggestions?

If I had a dead caliper in the rear ( would it effect both wheels)? My experience tells me it should only effect the wheel with the bad caliper. Altho I'm not sure how things work with this abs control module....

Here a video of detailz


Any help! Thanks guys!
 

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2004 ESV
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Definitely a strange issue. With the brake booster being assisted by the power steering pump, is everything ok with the power steering? I didn't hear any whine in the video, but how do the hoses look? Any leaks? Are they hooked up in the right spot? As I recall, I don't think you can cross the two pressure lines, as the nut that held the lines on were different size, but I don't remember.

It definitely seems like a brake proportioning valve type issue. Not sure if that is handled by the ABS unit or not. It could very well be the ABS module, but I would think you would have things like the ABS light on, and have issues surrounding the stabilitrak and the traction control.
 

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Discussion Starter #3
Definitely a strange issue. With the brake booster being assisted by the power steering pump, is everything ok with the power steering? I didn't hear any whine in the video, but how do the hoses look? Any leaks? Are they hooked up in the right spot? As I recall, I don't think you can cross the two pressure lines, as the nut that held the lines on were different size, but I don't remember.

It definitely seems like a brake proportioning valve type issue. Not sure if that is handled by the ABS unit or not. It could very well be the ABS module, but I would think you would have things like the ABS light on, and have issues surrounding the stabilitrak and the traction control.
I did forget to mention. Stability track and ride control lights are on - I believe this is due to the ( air ride ) compressor not working.......

Abs light is on - I get codes for the right front wheel speed sensor ( I'm fixing this next day off )

I also get a code - c0288 ( abs code )

Power steering works great!
 

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2011 CTS4 Coupe, 2014 ELR, 2018 XT5 AWD
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You might need to have the ABS unit blead.
This is not a regular brake bleed. It requires a scan tool with software.
588932
 

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I don't think air ride will cause any issues with stabilitrak. I say that because the first 6 months I had my Escalade, I had no air compressor, and the rear shocks were kaput. No stabilitrak issues. I did have to replace the front wheel bearings, but not because of shock issues.

Interestingly enough, the code comes back with this;

C0288 CHEVROLET Possible Causes

Faulty Master Cylinder Pressure Sensor
Faulty Yaw Rate Sensor/Lateral Accelerometer

Second cause wouldn't have any effect on the brakes

With you getting a used ABS module for $10, it couldn't hurt to install it. You will most likely need to bleed the ABS unit via the Tech 2, or some other compatible scan tool.
 

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Discussion Starter #6
I don't think air ride will cause any issues with stabilitrak. I say that because the first 6 months I had my Escalade, I had no air compressor, and the rear shocks were kaput. No stabilitrak issues. I did have to replace the front wheel bearings, but not because of shock issues.

Interestingly enough, the code comes back with this;

C0288 CHEVROLET Possible Causes

Faulty Master Cylinder Pressure Sensor
Faulty Yaw Rate Sensor/Lateral Accelerometer

Second cause wouldn't have any effect on the brakes

With you getting a used ABS module for $10, it couldn't hurt to install it. You will most likely need to bleed the ABS unit via the Tech 2, or some other compatible scan tool.
I have a scan tool capable of ABS bleeding - however when I try to bleed ( the scan tool ) refuses to do so until codes issues are fixed..... As soon as I clear the codes ( the c0288 comes right back )....... Iv had 2 different Master cylinders with 2 different brake pressure switchs - the only thing I haven't changed is the yaw sensor. I. Gonna make my way back out to the salvage yard and see if I can find one...... Someone said when I change it I gotta take it to the dealer to have it reprogramed.
 

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C0288.
5 volt reference out of range.
Look for a short to ground on the 5 volt supply to the master cylinder pressure sensor, lateral acceleration sensor or yaw rate sensor.

588933
 

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The code points to a wiring issue but if a sensor had a 5v short to ground it would cause the same fault. I would disconnect all the sensors and measure the 5 volt to see if it is still there. If it isn't you need to look for a wiring fault. If it is, connect the sensors one at a time to see which one pulls the 5V down
 

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Discussion Starter #10
The code points to a wiring issue but if a sensor had a 5v short to ground it would cause the same fault. I would disconnect all the sensors and measure the 5 volt to see if it is still there. If it isn't you need to look for a wiring fault. If it is, connect the sensors one at a time to see which one pulls the 5V down
Good this will be the next thing I do. I may try to do this tonight when I get home......... The next 3 days our 14 hour shifts then I'll be off. I appreciate your help and will update you soon.....


Side note...... The main reason I do not fill this is a ( air in the line ) situation...... How did air get in the lines with the truck just setting - iv personally never seen air in the lines cause a pedal to go directly to the floor but there always a first...... ( Why is it just the front line ) ( rear brakes is effected ) thanks again friend.
 

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Discussion Starter #11
The code points to a wiring issue but if a sensor had a 5v short to ground it would cause the same fault. I would disconnect all the sensors and measure the 5 volt to see if it is still there. If it isn't you need to look for a wiring fault. If it is, connect the sensors one at a time to see which one pulls the 5V down
I'm guessing the pressure sensor is the ( sensor ) inside the master cylinder reservoir ? If so I checked it with truck running - I have 13.7v there? I'll check other in next day or so. Thank you sir 😊
 

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The sensor in the reservoir is rather brake fluid level sensor. It is not the pressure sensor.
 

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Discussion Starter #13
The sensor in the reservoir is rather brake fluid level sensor. It is not the pressure sensor.
Yea I was kinda thinking that..... Was wondering how that thing could detect pressure.... I'll update you in the next day or so...... That was dumb of me
- theses 14 hour days are killing me
 

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I really don't know what I'm talking about but I'll add this....

I just did calipers rotors and pads on 2 trucks. Was expecting a firm pedal but on the Escalade I got just a tad bit of firmness and in my Honda it was exactly the same pedal feel. A mech friend of mine says at the age I should have replaced the banjo bolt lines as they will collapse on the inside and not give the pressure needed to really firm up the pedal like I was expecting.

Do you maybe have some collapsed lines or half collapsed lines somewhere in the system?
 

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Discussion Starter #15
I really don't know what I'm talking about but I'll add this....

I just did calipers rotors and pads on 2 trucks. Was expecting a firm pedal but on the Escalade I got just a tad bit of firmness and in my Honda it was exactly the same pedal feel. A mech friend of mine says at the age I should have replaced the banjo bolt lines as they will collapse on the inside and not give the pressure needed to really firm up the pedal like I was expecting.

Do you maybe have some collapsed lines or half collapsed lines somewhere in the system?
In my experience a collapsed line causes the caliper to stick ( stay engaged ) I have a 84 chevy and it has all original lines except one - it collapsed and the cal stuck! Thank you sir
 

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The best way would be a scan tool that can access the ebcm (abs computer) and find the brake pressure sensor data
 

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Discussion Starter #18
The best way would be a scan tool that can access the ebcm (abs computer) and find the brake pressure sensor data
My code reader will ( turn on and off the pump - it will bleed and do other things ) I wonder if it can see the data -
 

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Discussion Starter #20
The best way would be a scan tool that can access the ebcm (abs computer) and find the brake pressure sensor data
I Kno I can turn the pump on with the scan tool - iv done it.... I wonder if I did this and cracked the bleeder - if it would bleed.
 
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