Car starts when I press the brake pedal! [Archive] - GrandAmGT.com Forum

PDA

View Full Version : Car starts when I press the brake pedal!


DoCDooM
05-25-2008, 04:31 PM
Now here's a weird one my friends and I am in a true quandary so I hope somebody can help me out.

FYI 2002 Grand AM GT RAM Air 3.4 L engine NO MODS at all.

I just had my oil changed and went to reset the change oil light which I have done at least a dozen or more times in the past 5 years so I know I was doing it right.

After the oil is changed, drive the car a couple of blocks, shut off, put foot on brake pedal, put ignition in "ON" position but do not start, press gas pedal 3 times and I get 3 dings, the light goes out and is reset.

This problem literally "started" today LOL.

This time around there was a real problem, I put my foot on the gas turned the key and as soon as it went to the "ACC" position the engine started cranking and continues to do so until I shut off the ignition or move the key to the "ON" position after which the car starts.

The starter is not cranking after the engine starts or when the ignition is "OFF".

WARNING! TECHNICAL INFO below:

I unplugged the ignition switch and monitored the large yellow "START" wire on the harness, any time I press the brake pedal a small voltage (about 3 volts) appears on the starter wire.

This happens regardless of whether or not the ignition switch is plugged in so the switch is not the problem.

There is no switch on the brake pedal assembly where the starter wire passes through it so it is not a faulty neutral safety switch.

The problem does NOT appear if the car is in gear, just park and neutral so the neutral safety switch is working properly.

The voltage on the starter wire appears when the brake is pressed no matter what I do.

There are no DTCs (trouble codes) being issued by the on board diagnostics system (I have a reader YAYY)

OK Back to normal info:

So first and foremost something is wrong with my starter circuitry and it is somehow being affected by the brake circuitry.

This worries me greatly as some engineer at GM must be a complete idiot or was paid to design this thing to fail, in either case it is a serious danger.

I cannot reset my "Change Oil" light until this gets fixed.

I am going back to the Haynes manual now but it is sorely short on electrical drawings concerning PassKey, PassLock, radio and starting system wiring information and drawings (I wonder why?)

Please, if anyone has some answers I would love to hear them.

Thanks.

Dan

cardude007617
05-25-2008, 06:18 PM
wow, i cant wait to hear about what made this happen....

tenspeed
05-25-2008, 11:12 PM
Do the automatics require a foot on the brake pedal before moving the gear selector lever?

I have a manual. My 'o2 has a button in the drivers side fuse box to reset the oil life monitor.

lone_wolf025
05-25-2008, 11:24 PM
Hmm so 3 volts everytime you hit the brakes. There's gotta be a crossed wire somewhere. I'd tell ya to eyeball all the wiring you can where the power is distributed for the signal for the brake lights. I'd say disconnect the brake light switch and see what happens just for fun. Also seeing as how its 3 volts its gotta be a signal wire rather than a power wire.

I know you said there is no crossing of wires, but is that conclusion formed from actual visual inspection, or simply checking the diagrams? If its the later, visually inspect any and all wiring around the pedal assembly, just in case something got pulled or snagged somehow.

cardude007617
05-25-2008, 11:29 PM
Do the automatics require a foot on the brake pedal before moving the gear selector lever?

I have a manual. My 'o2 has a button in the drivers side fuse box to reset the oil life monitor.

they do. isnt that called shift lock or something?

tenspeed
05-26-2008, 06:51 PM
Since you have to step on the brake, I would assume that voltage would go to a solenoid to release the gear lever. Usually when you have a rogue voltage, it's a indication of a bad ground connection causing feedback through a load, like a brake light bulb.

It probably won't help but make sure all you brake light bulbs work.

awfulwaffle
05-27-2008, 02:58 PM
Since you have to step on the brake, I would assume that voltage would go to a solenoid to release the gear lever. Usually when you have a rogue voltage, it's a indication of a bad ground connection causing feedback through a load, like a brake light bulb.

It probably won't help but make sure all you brake light bulbs work.

GM may be in for some serious trouble if burnt brake light bulbs can cause these cars to crank when the brake pedal is pushed.

SSRacer
05-27-2008, 05:42 PM
I always just hold down the reset button with the ignition ON until the light flashes and then goes off. What's with all the brake pedal crap?

awfulwaffle
05-27-2008, 08:20 PM
I always just hold down the reset button with the ignition ON until the light flashes and then goes off. What's with all the brake pedal crap?

03-05 GA's dont' ahve the reset button

SSRacer
05-28-2008, 06:31 AM
I did not know that.

But he says he has an '02.

awfulwaffle
05-28-2008, 06:41 AM
hm, may be the 02-05's then

SSRacer
05-28-2008, 10:54 AM
Mine is an 02...I have a reset button.

Unless it was a midyear change, I got mine in Sept. '01, so it was a very early '02.

cmtapanes
05-28-2008, 12:12 PM
I have a 99 GA/SE and I do have the reset button but you can also reset the oil light by pressing the break 3 times. I believe that's on all GM cars.

hass
05-28-2008, 05:05 PM
I have a 99 GA/SE and I do have the reset button but you can also reset the oil light by pressing the break 3 times. I believe that's on all GM cars.

I reset all of my dash lights.. tire pressure, tire pressure, etc... through the reset button, no brake pedal stuff.
'99 GT.

DoCDooM
05-28-2008, 10:10 PM
I did not know that.

But he says he has an '02.

Hello All,

Thanks for the input, responses and opinions.

My GT is an 02, it has the reset button but that only resets the tire pressure timer (yeah it's just a timer) along with the "Service Vehicle" light which gets set off by burnt lights and non-critical issues but not the oil light, that HAS to be reset as described with the brake pedal.

I had the engine washed (low pressure non-caustic detergent spray and rinse) about an hour before the problem appeared.

The problem did NOT appear immediately.

About 5 hours later (sitting in a heated garage) the problem disappeared and has not returned (WHEW!)

Still I am concerned that the brake pedal can in ANY way cause the starter motor to engage, that is just plain nuts and stupid under ANY circumstances.

By rights you should be able to pretty much submerge the whole car and still not cause the starter to engage, water just doesn't carry that much current at a lousy 12 volts.

An engine wash should certainly not cause such a thing to happen.

I have yet to find out what might have caused the problem but whatever it was it was under the hood and was not caused by crossed wires, there are no mods on this car, just properly executed repairs (something that I've found is increasingly rare at dealerships lately by the way).

I've looked over the entire engine bay and found no frayed or damaged wires, no cracked hoses, no corrosion which might cause short circuits or crossover of low voltage sensor signals et-cetera all I found was the typical battery terminal scum which I clean every 6 months or so.

I live in Alberta so the car is exposed to some pretty hairy temperature and humidity changes all year long, hence the attention to corrosion.

The Haynes manual was as I described, sorely lacking in electrical details surrounding the starting system so it was no help.

A factory schematic would be a great help, if anyone knows how I can get my hands on one I promise to report back with more details after I get a better education.

FYI I'm an Electronics Technologist with 25 years worth of experience, even GM's electronics, while hideously over complicated, are still pretty simple circuit systems, so if anyone can find this it would be Yours Truly :)

Cheers,

Dan

SSRacer
05-29-2008, 07:45 AM
My GT is an 02, it has the reset button but that only resets the tire pressure timer (yeah it's just a timer) along with the "Service Vehicle" light which gets set off by burnt lights and non-critical issues but not the oil light, that HAS to be reset as described with the brake pedal.

We are talking about the "Chane Oil" light, correct? I reset mine every time with the reset button on my 02 GT.