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Brake light alarm and code PO105

Tiny
GEORGE OBERMAYER
  • MEMBER
  • 1997 MERCEDES BENZ S500
  • 5.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
Blew a rear brake line, replaced both rears and bled the brakes. Now have a brake light on and alarm when the car moves. Have a po105 code will not go away.
Thursday, February 28th, 2019 AT 4:47 AM

6 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,347 POSTS
Hello,

It sounds like the brake booster has gone out. Can you do me a favor and with the engine off, remove the vacuum check valve from the booster, you should hear vacuum escaping. Please report back.

Ken
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Friday, March 1st, 2019 AT 1:33 PM
Tiny
GEORGE OBERMAYER
  • MEMBER
  • 3 POSTS
I found the vacuum tube to the map sensor broken. Replaced, scanned and all dtc cleared. But I still have the brake light on and alarm when moving but goes off when fully stopped. I am thinking it's a speed sensor.
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Sunday, March 3rd, 2019 AT 7:48 AM
Tiny
GEORGE OBERMAYER
  • MEMBER
  • 3 POSTS
What's wired is I never had the check engine light on.
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Sunday, March 3rd, 2019 AT 7:50 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,347 POSTS
Does the engine seem to run okay? A bad MAF sensor can cause this issue as well. Here is a video and diagrams below to help you get the job done:

https://youtu.be/QOMiXhx2hbI

Check out the diagrams (below). Please let us know what happens.
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Monday, March 4th, 2019 AT 10:16 AM
Tiny
GEORGE OBERMAYER
  • MEMBER
  • 3 POSTS
I can hardly see the writing on the diagrams, but I know my mass airflow sensor is on the throttle body right on top of the motor. I've replaced it already after I repaired the map sensor plastic tubing by putting a new hose on it longer. All of my dtc's are zero but I still have the brake light and then alarm any time that I throttle up or anytime at the rolling.
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Tuesday, March 5th, 2019 AT 9:30 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,347 POSTS
If you click on the diagrams do they enlarge? Is the brake fluid level okay because the alarm will sound if the fluid is low? Can you check the ABS wheel speed sensors to see if one was left off when doing the job? Also, we can scan the ABS to see what comes up. Here is a video that shows how:

https://youtu.be/rTtAnsOlZU4

Please run down this guide and report back.
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Tuesday, March 5th, 2019 AT 9:36 AM

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