Seems that some times my 07 base c6 auto thinks I'm pressing the brake when I'm not and not pressing the brake when I am. This only affects the brake lights and causes the computer to disable active handling.

This is intermittent. Some times I go weeks without an issue but when I went to Laguna seca a few weeks ago it did it on every session, of course.

Anyone see this before and know the cause?

 

Normal to a degree, and just depends on the wear to the brake sensor forks, to pedal shaft.






So the low down, is the sensor is not an on/off switch, but has different ohm readings for the movement of the pedal.
Due to this, the BCM has to learn the reading of the sensor ohm reading at pedal rest, and then being pushed down to just to start to engage the brakes to turn the brake lights on.
This is done with a Tech II tool, and is call the BPS relearn.

So since the BPS is only about $30, and it plastic forks to metal pedal shaft do wear (to change the base line ohm readings that the BCM is using), some time you can get away with just doing the BPS relearn, but bet to just replace it, do the BPS relearn, and remember to grease the forks and pedal shaft, so the new sensor forks don't wear so rapidly isntead. Also, when doing the pedal push portion of the relearn, don't go buck wild on the pedal push to learn the BCM the ohm value of the pedal way down. Just push the pedal down until you just start feel the brake pedal build up light presssure, and let the BCM learn that sensor oem value.

Short of the pedal sensor being the problem, could just be the rear light main connector at the back of the car in the rear fender void area.

To get to the rear light connector, remove the inner passenger tail light, and it will be in on the cabin wall and down to disconnect it, clean and dielectrical grease the connector pins, and reconnect it.

Good shot of the rear light connector with the bumper removed, and its the connector on the right hand side that is coming through the back wall of the cabin wall for the rear fender. It's hanging down since it been disconnected from the fender lights, but is normally higher and attached to the back cabin wall where it comes through the wall.

 

Dano
Interesting as when I used my Tec II to relearn the BPS for my 2005 there was no brake pedal pushing asked for? simply take the foot off the brake and set the emergency brake , wait and relearn successful ? Yep still fighting this issue.
Thanks
Ted

 

BCM stop relay in the large one on the front side, to the lower left.



Remove it, start the car, and with someone pushing the brake pedal down, check the coil side of the relay pins on the BCM, to make sure it sending 12 volts through the two pins. Hence BCM energizes the relay coil, to send the 12 volts to the brake lights.
If you are getting 12 volts on the relay coil side, then double check the other pins to make sure you have 12 on the 30 pin, and jump out the 30 pin to the 87 pin with someone behind the car to look at the brake lights.

If all is good, then check the relay next. Hence 12 volt on it coil side, and them continuity through it secondary side with the coil energized.

86 is BCM sending power to the relay coil, 85 is the ground on the other side of the coil, which pulls the seconday in to connect them to send power to the stop lights.
30 is constant power from the BCM when the car is started on the secondary, and 87 is that power to the tail lights when the coil is energized by the BCM.



Also, with tech II after BPS relearn, go into BCM data, and look at brake pedal position to make sure that the wiring from the BPS to the BCM when the pedal is pushed. This weeds out at least the pedal sensor working with the BCM, then the Relay coil side tells you if the problem is BCM energizing the relay coil to begin with.

So Tech II will tell you if the BCM is seeing the signal correctly to begin with.
12 volt on 86 will tell you if the BCM is energizing the relay correctly on pedal push.
Power on 30 with the car started tells you if the relay is has power on the ACC constant (or fuse is blown), and jump across 30 to 87 is putting power to the brake light wires, and will tell you if the problem is in the wiring back, the connector in the rear fender void, or even just the stop light connectors at the bulbs.
Note, check the bulb connectors on the ground side of the tomb stones, to make sure that the ground wire to the ground chassis is still connector or not.