JPod

Hi all,

I had such great luck on here with my first post I thought I would create a second post for a new issue, I hope I am not creating a duplicate post, I did look and could not find anything that matches this issue.

I have a 1999 Tahoe with push button 4WD, column shift, 5.7L Vortec with about 195,000 miles on it, the trans and transfer case has been overhauled (prior to us owning it). Today I received a frantic call from my wife (they usually are frantic when it involves my wife and a car not working). She had been driving without issue, stopped to get fuel and then was not able to get the truck out of park.

After a few minutes on the phone with her I was able to get her going by having her turn the truck on and off wrenching on the shifter and depressing the brake peddle and generally jostling the shift lever. Apparently it happened again at our mailbox (why she decided to stop there instead of getting it in the driveway I will never know) and again after manhandling it was able to get it back out of park.

Now the car is home, I have given instructions to not take it out again (hope she listens) so I can look at it when I get home.

This is where all of the experts come in...

I am not sure what I should be looking at first or where to find it or how to identify what the issue is. Is this a mechanical bar/rod or is it electronic/magnetically locked, is there a switch that can be dislodged, or maybe it is something at the trans linkage end of things?

Your suggestions are most welcome.

JP

in2pro

Check the switches at the top of the brake pedal first make sure its working to activate the shift lock.... The next step is to open the steering column to see if the shift lock is worn... But I suspect its the switch at the brake pedal....

in2pro

A brief description and attached is the schematic of the circuit...


Automatic Transmission Shift Lock Control Circuit Description
The brake transmission shift interlock (BTSI) solenoid requires the ignition to be in the run or start position and the brake pedal to be applied before the transmission may be shifted from the park position.

With the ignition in the RUN or START position and the automatic transmission in the park position, battery voltage flows from the TURN/BU fuse 16, through CKT 139 (PNK) to the park/neutral position (PNP) switch. The PNP switch is closed in park which allows battery voltage to flow through CKT 275 (LT GRN) to the stoplamp switch. When the automatic transmission is in the park position, the stoplamp switch allows battery voltage to flow through CKT 1135 (DK GRN/WHT) to energize the BTSI solenoid. The BTSI solenoid is grounded through CKT 150 (BLK) to ground G200. With the BTSI solenoid energized, it will lock the automatic transmission in the park position.

When the brake is applied, the stoplamp switch will interrupt battery voltage flow and deenergize the BTSI solenoid. With the BTSI solenoid deenergized, the automatic transmission may then be placed in another gear which will cause the contacts of the PNP switch to open and interrupt battery voltage to the stoplamp switch.

JPod

In2pro

Is there a different name for the BTSI or do you have a part number? I am trying to find it at all the usual places and I am not coming up with a part by that name. I have not been able to recreate the issue as my wife described it, however I have seen in other forums where people had experienced similar problems when the cab of the vehicle got exceptionally warm...in our case my wife driving for an extended trip with the new heater core blasting out heat at full blast with full fan (just fixed this so she is enjoying her new heat in the low 30s we are currently having).

JP

in2pro

Have you inspected and verified the brake switch? the BTSI solenoid can go out but most likely its the switch or the wiring... the solenoid is a pretty simple item...again I don't want to discount it as the problem, but the brake switch is easier to check out....
When its activated you may be able to here it click....

check GM parts direct or give your local dealership parts department a call as this may be a dealer only item...

JPod

Yes, sorry I failed to mention that I checked the switch. It appears to be in good order, clean and in place solidly. When I depress the brake pedal the brake lights come on and there is an audible click when the connection is made.

hicksvilleshick

ok after that, are you able to shift the truck??? I can't remember which on it was but one of ours wouldn't shift out of park until you were on the pedal solid.

Is it possible she was trying to shift without her foot on the brake? (I'm not trying to imply anything here, I'm not sure how long you've had the truck)

If you can hear the lock disengaging from the brake pedal there should be nothing to prevent you from shifting, with the exception of the linkage.... ruling either of those out, your looking at the column.


:chug:

JPod

So far I have not been able to recreate the situation that my wife ran into twice in one afternoon.

To answer the additional questions this has been the daily driver for my wife over the past 4 years (we also owned a 96 and 98 Tahoe previously) so she has a good idea how to get it out of park, but good question since if she didn't know how to drive the truck this could be an (the) issue.

What I noted (or meant to note anyway) about hearing the brake switch was it sounds like an electrical connection is being made when the pedal is depressed, a slightly audible click). As I understand it the lock (BTSI solenoid) is in the column(?) so this is not the sound I am hearing, besides the sound is also evident when I depress the pedal while it is in neutral which would indicate that the sound is not the lock since it would already be disengaged given it is out of park.

I expect that I will be having to spend time with a parts guy at the Chevy dealer trying to get a part number for the BTSI solenoid, I think it may be starting to fail.

Any other suggestions are welcome or if anyone knows the part number for the BTSI (or a different name that it can be found at a parts store) so I can maybe find it outside the dealer.

in2pro

Is it possible she may have been trying to shift into gear before having the brake fully depressed ? (Maybe being in a hurry)
You might also try a lite spray of a dry lubricant on the switch... If your hearing the click its most working...but the lock could also be a bit sticky....
Before investing in the lock you might try gaining access to it first just to check it out... Maybe it just needs to be cleaned....

JPod

So I have now been able to recreate the problem.

I took the truck on a drive of about 45 minutes and when parked the shifter would no longer shift out of park. I let the truck cool down for maybe 30 minutes while my family and I went for a coffee (I am in Seattle so it is pretty much the thing to do). When I got back to the truck and started it up (now that it was cooled down a bit) it shifted just fine. By the time I got home after a hour or so I dropped it into park and attempted to bring it back out into reverse it was locked and would not budge. An hour or so later I went to check on it and it again was fine. This also happened to me on another hour long drive the other day that involved a few stops, this time rather than putting it into park I left it in neutral and set the e-brake...though I am not a fan of leaving the key in the ignition...

Suffice it to say it feel to me like there is some sort of issue with length of trip maybe warming up the area creating a situation where it sticks.

Any additional thoughts?

JP