Car starts without brake pedal being pressed...why?

[IGot2P]

I had this 2005 XLR delivered on Christmas Eve of 2024 and just drove it for the first time yesterday (04/13/2025). First I had put new chrome wheels on it, clay bared it, and cleaned it all up in general. The top worked fine for the first two days and then quit working. I just finished putting one new cylinder and a new pump in and it works fine now. My current problem is that sometimes when I try to start it the DIC says "Press Brake Pedal" or something like that. When I press the brake pedal it still does nothing unless (now comes the weird part) I open and close the passenger door two times and then it starts but without pressing the brake pedal. This does not always happen and usually it will simply start without pressing the brake pedal. I do have a couple more concerns/problems but let's just start with the "starting without pressing the brake pedal" and see if we can find an answer for that. BTW, I do have a Tech 2 if that helps.

Don

 

[justdennis]

What does the Tech2 tell you? Just a guess but maybe the vibration caused by closing of the door is doing something to a loose connection, maybe in the fuse box, check and clean all of those connections. Good luck

 

[luxuryrules]

The tech2 can display brake pedal position, would watch that while doing things like pressing and releasing the pedal, opening the door, etc. Bet you’ll see some intermittent data

 

[luxuryrules]

@IGot2P thanks for your patience - posting steps here in case anyone else ever needs to look up how to check brake pedal position. It's listed as Brake Pressure Sensor 1 (and in the doco sometimes referred to as Brake Pedal Position Sensor or BPPS) but is basically the sensor that tells the car the position of the brake pedal.

From the opening screen, select F0 Diagnostics > select your car > F4 Brakes > Hydraulic Brakes > F1 Data Display > F0 Electronic Brake Control Module > it will think for a moment while it establishes comms with the EBCM then you will see 3 items, one of which being the Brake Pressure Sensor 1. As you press the pedal you'll see the value change in realtime.

Don't do what I did my first time with a Tech2, car should be either running or in "On" mode and not just "Accessory" mode. Can hold the accessory mode button for 5-10 seconds and it will flip to "On".

 

[IGot2P]

Hey, thanks a bunch it was really appreciated. I have attached two images, one with the brake pedal not pressed and one with the brake pedal pressed all the way down. What exactly does those images tell me?
Don

 

[luxuryrules]

For the life of my I can’t find what the range is supposed to be, but mine is .49 not pressed and about 2 when pressed, so those values look ok: but open and close the door a few times while watching that value and see if it changes

 

[IGot2P]

For the life of my I can’t find what the range is supposed to be, but mine is .49 not pressed and about 2 when pressed, so those values look ok: but open and close the door a few times while watching that value and see if it changes

Open and closed the door many times but not change on the readings....original door thingy must have been a flute.

 

[luxuryrules]

Ok here we go: PIC3079

Recommendation is performing a brake pedal position sensor calibration.

 

[IGot2P]

Ok here we go: PIC3079

Recommendation is performing a brake pedal position sensor calibration.

It worked like a charm...thanks a bunch. Now I am curious to see if it fixed my cruise control.
Don