Service brake system message

Tiny
NANRIFE
  • MEMBER
  • 2004 GMC ENVOY
  • 4.2L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 250,000 MILES
Service brake system message appears keeping the car from starting. Will not even crank over or shift from park. Cycled keys and it worked with no problems, only for a little while. Now it has completely shut off and will not start at all, even after cycling the keys. Left alone for four months got in turned the keys message was gone and it started, ran for maybe three minutes and shut off again after service brake system message reappeared.
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Tuesday, July 24th, 2018 AT 6:12 AM

3 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi and thanks for using 2CarPros. Com.

The most common reason for that message to come on is due to low brake fluid, and it's the easiest thing to check. I have attached two pictures for you to see. The first is a front view of the master cylinder and the second is a side view. First, open the hood. The master cylinder is located on the driver's side, mounted to the firewall.

There is a plastic reservoir on the master cylinder (see picture 2) with a plastic screw cap on it. Clean any dirt from the reservoir and see if the fluid is to the max or full line. If it is low, top it off with the proper fluid (see the cap for dot 3 or dot 4 brake fluid requirements). Do not put anything in there other than brake fluid which meets the manufacturer's requirements.

If it is full, try this. The second picture I attached is from the side. Note there is a square electrical connector at the bottom of the reservoir. That is a sensor which is designed to let you know when the fluid is low. Carefully remove it and inspect the connections to make sure they are clean and undamaged. If they are good, gently tap the side of the reservoir with a light screwdriver so as to not damage the reservoir but hard enough to possibly release a stuck switch. Reconnect and see if the light is out.

Note: If the fluid is excessively low, you need to check for leaks. If the car starts, do not drive it until you are certain you have a solid brake pedal.

I hope this helps. Let me know what you find or if you have other questions.

Take care,
Joe
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Tuesday, July 24th, 2018 AT 6:54 PM
Tiny
NANRIFE
  • MEMBER
Thanks for the help. Unfortunately that was not the problem. Still having the same issues. Forgot to mention in my previous question that the rpm gauge goes nuts when the car is only in the on position up to 2,500 then back down. Sometimes bouncing up and down. Other times just hanging out at 2,500. When it does this it does nothing when I turn the key.
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Saturday, July 28th, 2018 AT 4:52 AM
Tiny
ASEMASTER6371
  • EXPERT
Good afternoon.

If the dash is going crazy, either the cluster itself has an issue or possibly the body control module. The body control module does control the starting and may be related to both issues.

As far as the brake message, I would have the code checked for the light. There is a fault code set for the system in the ABS module. A parts store should be able to read this for free for you.

Roy

https://www.2carpros.com/articles/abs-warning-light-on-easy-repair-guide
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Sunday, July 29th, 2018 AT 11:03 AM

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