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08 Chevy Equinox brake lights & shift interlock problem


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superprohero
Novice

Apr 12, 2021, 10:14 PM

Post #1 of 9 (1727 views)
08 Chevy Equinox brake lights & shift interlock problem Sign In

2008 Equinox Sport 3.6. Bought nonrunning (two spun rod bearings, sat about a year). Just rebuilt the engine and got it back in, starts and runs fine but there's a weird issue with the brake lights. Besides the AWD traction control lights being on there is this issue where when you start the vehicle the brake lights are on(including 3rd brake light) with foot off of the brake. When you push on the brake pedal the brake lights go out but come back on immediately as if you just pressed the pedal. They stay on as long as the brake is depressed as they should. When you let off the brake the brake lights go out, as they should, but after 5 seconds they come right back on. It is almost exactly 5 seconds every single time no intermittent behavior. The odd thing is when you let off the pedal and the 5 seconds pass, there is an audible click in the shifter area as soon as the lights come back on. I took the console apart and it's coming from the shifter interlock solenoid that blocks the shifter from being put into gear. When you pull up on the brake pedal with your foot there is no change so it seems it's not the brake light switch because it activates the shift interlock solenoid and brake lights every time. I took the shifter interlock solenoid out and tested it with a 12 volt jumper box and it actuates just fine and is strong. I've unhooked the battery pos and neg cable several times. Replaced the tail lamp/brake lamp bulbs with new. I can't figure out why the brake lights stay on and even stranger come back on 5 secs after releasing the brake pedal. Also if anyone happens to know, since I had the motor out, does this have to have the steering angle calibrated even though it's a total hydraulic system on the 3.6?
Thanks in advance.


superprohero
Novice

Apr 12, 2021, 10:16 PM

Post #2 of 9 (1723 views)
Re: 08 Chevy Equinox brake lights & shift interlock problem Sign In

Also I found a GPS tracker with a starter solenoid disable relay under the drivers knee bolster panel but it's evidently no longer in use. As stated it starts and runs fine.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Apr 13, 2021, 3:27 AM

Post #3 of 9 (1709 views)
Re: 08 Chevy Equinox brake lights & shift interlock problem Sign In

The shift interlock operates from the brake lights so that is operating normally. The brake lights are managed by the BCM so that is where the problem may lie.

You probably need a dealer level scan tool to get to the bottom of this. I also noted that the brake light switch is a 3 wire, 5v reference sensor capable of giving varied degrees of brake application so there could be an issue there also.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



superprohero
Novice

Apr 13, 2021, 5:52 AM

Post #4 of 9 (1701 views)
Re: 08 Chevy Equinox brake lights & shift interlock problem Sign In

Thank you Hammer. My suspicions where leaning towards the BCM. I pulled some parts from a local Pull-a-Part from a vehicle identical in every way to this one. What are the chances I could use that vehicles BCM without any programing? If it is the varying brake pedal position it's going to need calibrated I understand. Thanks again.
Side note: I will be posting back with the resolution for others who run across this with a similar issue.


(This post was edited by superprohero on Apr 13, 2021, 5:55 AM)


Hammer Time
Ultimate Carjunky / Moderator
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Apr 13, 2021, 5:57 AM

Post #5 of 9 (1697 views)
Re: 08 Chevy Equinox brake lights & shift interlock problem Sign In

Your chances are slim to none on not needing programming.
I would expect it would at the very least need the VIN# programmed in.

You really shouldn't try to fix this by throwing parts at it. That will only serve to empty your wallet. You need a scan tool to see exactly what the pedal position sensor is telling the BCM and what the BCM is doing about it. It could just as easily be a bad pedal position sensor.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Apr 13, 2021, 7:26 AM

Post #6 of 9 (1691 views)
Re: 08 Chevy Equinox brake lights & shift interlock problem Sign In

Lots to read here see a partial reason 1st post. Two cars sat for a year. Anything "brakes" would rust and particles would mess up magnetic anything for each wheel speed.


Not sure on the shift interlock if interiors were full of wet air, dripping everywhere + can't dry out properly for a year no telling what items messed up?


T



superprohero
Novice

Apr 13, 2021, 6:15 PM

Post #7 of 9 (1667 views)
Re: 08 Chevy Equinox brake lights & shift interlock problem Sign In

Yea there's all kinds of stuff going on. Took it for a drive to get gas in it (1st time since it's sat over a year). Shut it off at the pump and it started and drove off fine. Got down the road and the ABS and traction control lights went out as if all was well. Thought maybe there were enough key cycles without an error so it removed the codes. Got closer to home and the ABS came back on. Shut it off at home then took it for a longer drive. Got out on the road and the ABS TC lights went out again as if all was well. Drove to a friends house and let it set outside running for about 20 minutes. Went to leave and before it could get out of 1st gear the check engine light came on and it wouldn't shift past 1st gear. Turned around, back to friends and scanned with a cheap little hand held and it put out P0752 Shift Solenoid A Circuit stuck open and a P0700 Transmission Control Malfunction. Cleared the codes and tried to drive it and it kicked the same codes and wouldn't shift out of 1st. It did this before when it got warm after I drove it to town. This thing has some issues!!
Reminds me of the 04 Cadillac CTS 3.6 I bought totaled and fixed. It would start and run if you took the ECM off and put it in the freezer for several hours, but wouldn't do jack once it was warmed up. This is typically a sign of a hairline crack in the ceramic circuit boards in those ECM's. Not saying my problem now is the ECM but it's odd that there's no trans errors when it's cold but seems to present itself when fully warmed up.
My sisters ex has a GM Tech2 and is a local GM dealer driveabilty mechanic so I'm going to try and get ahold of him over the next couple days to scan it for me. Suffering from buyers remorse now! Ha ha.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Apr 13, 2021, 6:24 PM

Post #8 of 9 (1663 views)
Re: 08 Chevy Equinox brake lights & shift interlock problem Sign In

The BCM play no part in the shift solenoids. The TCM does that. It only plays a very small part in the ABS also.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



superprohero
Novice

Apr 15, 2021, 8:50 PM

Post #9 of 9 (1624 views)
Re: 08 Chevy Equinox brake lights & shift interlock problem Sign In

Sorry this is long.
As far as the brake lights I agree and I'm feeling like it may be the brake switch/position sensor.
After the last episode at the friends house where it wouldn't shift out of 1st, I left it there all night and as suspected the following evening I cleared the codes and it started up fine and drove home fine albeit with the ABS and Stabilitrack lights lit like usual.

I forgot to mention when I 1st put a timing chain in this last summer, with the key in the run position, the same ABS Stabilitrack lights were on but when you turned the key to start there was nothing(no crank). I found online where some people could get it to crank and run if you connected a ground wire to the ECM chassis. So that's what I did back then and it worked!! Sorry I failed to mention that important piece of info!

So having it back home, and thinking of the ground wire I put on the ECM chassis, today I removed the battery, and battery tray and removed the large ground cable from the post on the apron/steel wheelhouse and used a Dremel mini wire wheel and cleaned the ground cable eye, threaded post it mounts to, and the nut on the washer side that contacts the cable eye. Put it back together and started it. Same ABS Stabilitrack lights on, let it warm up really good. Shut it off, disconnected the battery, disconnected the small ECM chassis ground and hooked the battery back up and it would not crank, again. Hooked the ECM chassis ground back up and it cranks and starts great! So I drove it extensively staying within a mile of the house and the ABS/Stabilitrack lights went out and the check engine light/stuck in 1st gear never happened this time. Even stopping 3-4 times at the house and letting it idle for long periods until the cooling fan kicked on and driving it more.

Due to the intermittent nature it's hard to pinpoint but the two times the no shift/check engine light presented itself was after driving it a decent distance and had it good and warmed up, yet letting it cool overnight and clearing the code the issue doesn't present itself again until it warms up. This leads me to think it's a break of some sort in the ECM. i.e. expansion from heat and contraction from cooling causing a connection and breaking the connection. And having to ground the ECM chassis seems to make sense it's the ECM but I could easily be wrong. It just seems to make sense. Still trying to get ahold of the guy with the TechII to see if he can uncover anything. I'm considering throwing an ECM at it and see what happens but I'm waiting on the TechII guy.






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