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Shift Interlock, Brake Lights Don't Work...

9452 Views 14 Replies 5 Participants Last post by  kailua bull
Here is the latest installment in the continuing saga of the deterioration of my bull...

My 98SE has been experiencing intermittent shift-interlock problems... that is, even with the brake pedal depressed, the car will not shift out of park. Sometimes it does, and sometimes it doesn't. Sometimes, when it will not shift out of park, if I rock the car forward, the car will shift out of park. Today, I have not been able to get it out of park at all. When I checked for operation of the brake lights, I found that they don't work, either.

So, I immediately suspected the BOO switch, and picked up a Motorcraft-branded replacement at my local parts store for $10.50 + tax. In 5 minutes, I had the switch replaced. However, this has not fixed the problem(s).

I've fooled with the harness to check it for opens/shorts, and it doesn't seem to have any problems (I made sure that there was good contact inside the harness and wiggled the wires around to make sure I didn't have an intermittent open). I checked all the pertinent fuses (stop lights, shift lock, etc.), and they were all in good shape. Now I'm out of ideas.

The weird thing is that this started happening with more regularity after I got the car back from having a front-end alignment. It hadn't had these problems for a long time, but over the last two or so weeks, I've been dealing with this more and more until today, when I've had no sucess in shifting the car out of park.

If anyone could direct me to some other things to check or point out where I've gone wrong during diagnosis and replacement of the switch, I'd appreciate it.

Many thanks in advance,
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Are you parked on a slight slope (like an angled driveway or a hill)? That could cause the parking pawl to hang to the tranny and not disengage. The best thing to do is when you park your car, shift into neutral and set the parking brake. Then let it settle and then shift into park. And when you leave, you should shift into gear first, then release the parking brake.
I know what you're saying about the parking pawl... I've noticed that parking on an angle causes the transmission to be hard to shift from park. This is also true if I back the car up against a curb and then shift into park. Basically, any position that causes a force to be exterted against the drive wheels when the thing is shifted into park will do it once the car is allowed to roll after shifting. I was always afraid of snapping a shift cable when I'd be dumb enough to park like that (and it's like, I never learned, either). In these cases, the shift lever is hard to move, but it is still allowed to move.

Unfortunately, this time the car is parked on a level spot, and my back wheels aren't against anything. There is a major difference in the way the shift lever feels when I try to shift out of park... Right now, the lever feels as though there's a metal collar around the thing that will not let the lever move down through the gears. I feel as though if I try to force it that I will break something. I can't even pull the lever back as much I am able to normally.

Thanks for reponding, Qwertz... lemme know if you come up with anything else - I appreciate it greatly!

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I have a 98 Sable, and I've experienced similar problems, but only on cold days (30 and below). I've never experienced it when it gets a little warmed. I like to attribute it to the gnomes being a little cold. Takes them a second or so to get warmed up enough to shift the car. Anyway...as soon as the engine warms up a bit, the car shifts easily.

When I stop, I always hold the brakes down and engage the parking brake, then shift to park. It's much better for the tranny, as well as the torque converter. The only problem is that eventually the parking brake cable could potentially snap...

Sorry I'm not of much assistance with your problem, but I also agree on the drop it in neutral, engage parking brake, then put it in park practice. I always do that, too unless I park on a level surface. :)

I take it the thing you replaced is the sensor for the car to know when the brake pedal is pressed? If your brake lights aren't coming on still there is clearly a problem with that somehow... I will check my Ford service CD and see if I can find anything useful. :)
Sounds like you're pretty knowledgeable and have checked most of this stuff, but here's what the service CD says to check for (in this order):

Brake Lights
Check Fuse 14
Test Circuit 10 for a short to ground
Test Circuit 10 for an open
Test brake pedal position switch
Test Circuit 810 for a short to ground
Test Circuit 810 for an open
Test for B+ on Circuit 1087C
Test Fuse 57
Test Circuit 1087C for a Short to ground
Test Circuit 1087C for an open
Test circuit 57E for an open

If you would like more info about any of these items, let me know and I'll give you what I've got. :)
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Thanks to Jason and 'spunk...

Something that I forgot to mention when I cobbled together my original post is that during this whole period of the haunted shift-interlock and brake-lights thing, I've also noticed (back when I could still DRIVE the car) that when I want to disengage cruise control by tapping the brake, it has been taking substantially more pressure on the brake or a series of taps to get the cruise control to disengage.

This whole thing really really really smacks of BOO switch failure. Why replacing it didn't take care of it is beyond me... Jason, if you want to provide more info from the service CD on those topics, I'm all ears...

It seems like if letting the car warm up would allow me to shift out of park, that I would have an intermittent short or open that goes away when heat expands the wires enough to re-establish contact. Guess I"ll go let the car warm up and see...

Many thanks again,
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Um... k...

So, I went outside and started the car this evening, expecting to leave it run for awhile to see if letting it warm up would help the situation. The car shifted right out of park without me waiting.

I was talking to a friend of mine earlier after this, and he mentioned that if the original BOO switch was intermittent, and the car's computer didn't think it was there, when the new one was installed, the computer needed a few starts and/or some run time to "get used to" the switch being there. Does this seem plausible?

Also, I can't use the "turn the car on without starting and shift into neutral before starting the engine" trick, because the car will not allow me to shift out of park unless the engine's running, even when the BOO switch is apparently working. Also, there's no dice in leaving the car in neutral with the emergency brake on when I turn it off because then I can't lock the ignition switch and remove the key.


Thanks again,
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It gets better...

This morning (Monday), I decided to take the car to work... an easy, 7-mile drive down the highway. I got in, turned the key, shifted out of park, and drove off.

When I got to the highway portion of the drive, I decided to use my cruise control, but when I pushed the buttons, it wouldn't engage. So, now the car is exhibiting symptoms of a BOO switch stuck "on" instead of "off" as before... but when I got to work, I checked for the brake lights being stuck on. They weren't.

Criminy... this thing's worse than the stuck door-latch thing I went through a couple years back. At least all that took was a shot of WD-40.


Thanks again,
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Sorry - ran out of time to do this today. I'll sit down and get some more info for you tomorrow night... i gotta go back into work - this stupid new computer virus is causing me all kinds of problem... :angry: :rolleyes:

Have you tried just 'cracking' the key, shifting it to neutral, then starting it? What I mean by 'cracking' the key is turning the key halfway between the locked position and the first accessories position. Nothing should come on, but the steering wheel should release.

The problem arose shortly after I sold the car to my dad a couple months ago. He struggled with it for a while, but has gotten used to doing this routine. I'd like to know the permanent fix, but at least this gets him on the road. The car is an '01 SE.

Hope this helps.

Well, since you need the info, too now - I'll post it tonight... I figured maybe he didn't need it anymore since there wasn't a new reply. :)
Okay, so the plot thickens...

Lately, my car has been shifting out of park without difficulty. On long trips, such as the ones I've been making lately, when I leave the car, I'll put it in neutral and amazingly, now I'm able to lock the car, even with the car in the neutral and the key in the ignition. Also, the brake lights work, okay, but the cruise control has stopped working altogether.

I swear the car's haunted... lol.


Thanks again,

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I'd suggest an Old Priest and a Young Priest.... and beware of pea soup.... Actually, it started off sounding like a problem my 98SE was having, but then yours became a lot messier. :blink:
Interesting thing happened to my dad's '01 SE. After I replaced the master cylinder, he no longer needs to do the little trick to get it out of park. It's been two weeks now and everything is working fine.

Try flushing the brake system. You know what they say, "When all else fails, try cleaning the ash tray!" Good Luck.
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