2000 Chevy Trailblazer Engine Shutoff When Brake Is Pressed

djtall11

I have a 2000 Chevy Trailblazer with 156k miles.
Within the last month when at a stoplight or stop sign or even when I hit the brake backing into the driveway, the car's engine will shutoff. The only way to fix is to put the car in park and then turn the engine back on turning the key in the ignition. The problem does not happen all the time, which is making it frustrating and harder to diagnose.

I've been two different mechanics, both who have had the car for over a week. Neither one had the issue happen to them while driving it. They both checked for error codes, none appeared on the engine, gas pump, nothing. One mech did a smoke test and found some leaks which he fixed, but the still occurs.

The car run great otherwise. No check engine lights or other apparent issues. Battery is 3 months old. Had a good tune up in last 2 months with no major issues.

Any idea what this could be? It's my wife's primary car so I'm concerned about her driving it since we don't know what's causing this.

djtall11

Some more detail: Was driving it this weekend and the issue happened twice.
I was braking at a stop light when the engine went dead, the battery light came on, the dashboard lights stayed on and the power steering died also. Had to come to a complete stop, put the car in park and then turn the engine back on with the key.

Mr_Shiftright

It's possible the brakes have nothing to do with it, and that the truck is just stalling at random. With a diagnosis, you always have to go back to basics, and the idea of the brake light circuit being part of the problem might be a false lead.

So none of your mechanics was able to extract any codes or freeze frame data?

djtall11

In extensive driving, by both myself and my wife the problem only happens when the brake is pressed. Another way to look at it is that it happens when the accelerator is NOT pressed.

Nope. Two different mechanics, neither one got any codes or data.
Thanks Mr_Shiftright

kyfdx

djtall11 said:

In extensive driving, by both myself and my wife the problem only happens when the brake is pressed. Another way to look at it is that it happens when the accelerator is NOT pressed.

Nope. Two different mechanics, neither one got any codes or data.
Thanks Mr_Shiftright

Maybe, something to do with the lockup on the torque converter? Not unlocking, causing the vehicle to stall?

Just an uninformed guess...

thecardoc3

Troubleshooting a problem like this first of all takes patience because you are only going to capture information during the failure. The random nature of issues like this makes that a real challenge all by itself, but with a good game plan a lot of ground can be covered each time the failure occurs. That of course reveals one of the biggest hurdles because you just cannot measure every possible cause and so this becomes a series of discovery and reset depending on what was proven to be OK or NOT OK during a stalling event.

kyfdx said:

Maybe, something to do with the lockup on the torque converter? Not unlocking, causing the vehicle to stall?

Just an uninformed guess...

Ideas like that are fine but need to be proven before just acting on them otherwise you are simply tossing parts at the problem and hoping. So how can someone put some leverage towards or away from such a guess?

For one, start by trying to pull codes from every module on the car, not just the powertrain control module.

@djtall11 When the engine stalls, what exactly does it feel like?
Does it simply stop running almost silently?
Does it kick and sputter as it dies?
Does it feel harsh and shake the whole car as if you forgot to step on the clutch in a manual transmission vehicle when you came to a stop?

If none of those, describe it please_________

The next thing that I need to know is under what conditions if any does the problem occur?
How far does the car need to be driven on average to be likely to experience the failure? Best estimates.
How long does the engine need to run to be likely to experience the failure?
What is the weather usually like when the problem occurs?
Does the car need to be driven, turned off for some period of time and then restarted?
When it stalls is it difficult to restart?
Is there anything else that works, doesn't work when the car quits before you attempt a restart such as power windows, radio etc.

Any details come to mind that I didn't ask about? _________

Now with all of that what we have done is set the stage to begin testing. I would likely start with the Tech II scan tool hooked up and in recording mode. I would be attaching a fuel pressure gage to monitor fuel supply. Plus I would have the digital storage oscilloscope attached and monitoring the following signals:
Camshaft position sensor signal.
Crankshaft position sensor signal.
Ignition coil command signal.
Fuel injection command signal.

I may or may not add other tools to monitor specific inputs or system voltage.

Now it's necessary to drive it and get it to act up, no real progress can be made until that happens.
What's worse is I can proabably guess what really is going on, but without proof you wouldn't know that the car was fixed and so you wouldn't trust it to go anywhere. The problem not occurring doesn't prove that it really has been repaired, it only proves that it hasn't happened again yet.

djtall11

@kyfdx
I'll have that checked. Thanks.

@thecardoc3
Car doesn't shudder, just quietly shuts down. The car has a bit of rough idle that usually goes away after driving for 5-10 minutes.

No particular weather conditions. Most times it has been dry. I've been driving on the road, hit the brake/foot off accelerator and the engine shutoff. I've also been idling in a parking lot after driving there and have the engine shutoff. The power steering does not work, the battery light on the dash comes on, and the dashboard and headlights stay on.

I put the car in park and immediately turn the key to start the engine. I have no problem starting the car again, happens immediately.