Shift Lock Override

[kestrel]

Hey folks - I've owned my '89 4WD for a few years and it suddenly started forcing me to push the shift lock override button 80% of the time from P to any other gear. Ideas? I tried searching the forum but couldn't find anything.

Happy spring!
Kestrel

[JDM VANMAN]

Could be the neutral safety switch? Just an unprofessional shot in the dark.

[timsrv]

When you're having the problem, have somebody check to see if the brake lights are working. Could be a problem with your brake light switch or your brake light circuit. The later model vans have a safety protocol that requires the brakes to be pushed before letting you shift out of park. It gets the signal from the brake light circuit. If it doesn't see brake lights, then it doesn't release the shift lock. Tim

[kestrel]

When you're having the problem, have somebody check to see if the brake lights are working. Could be a problem with your brake light switch or your brake light circuit. The later model vans have a safety protocol that requires the brakes to be pushed before letting you shift out of park. It gets the signal from the brake light circuit. If it doesn't see brake lights, then it doesn't release the shift lock. Tim

thanks tim! i'll check it out and get back to you.

[kestrel]

When you're having the problem, have somebody check to see if the brake lights are working. Could be a problem with your brake light switch or your brake light circuit. The later model vans have a safety protocol that requires the brakes to be pushed before letting you shift out of park. It gets the signal from the brake light circuit. If it doesn't see brake lights, then it doesn't release the shift lock. Tim

heya tim - checked it out and the brake lights are working fine when the problem is occurring. other ideas?

[timsrv]

If your brake lights are working when the shift lock is not, then I'm guessing it's a sticky solenoid. Take your shifter/console cover off and check the solenoid for ease of travel (you can work it back and forth with your fingers). If it has corrosion, dried soda pop, or whatever gumming it up, then try to clean and/or lubricate. A silicone spray would be the preferred lube here.

If it still doesn't work, then check for power at the connector where power is supplied to your shift lock computer from the brake light switch. It's the grn/wht wire in this connector (see the red arrow in the picture below). If you put a test light on this wire, it should go on/off with the brake lights.

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/electrical/IMG_3959_zpscarfhui5.jpg

If power is here, then check power from the shift lock computer to the shift lock solenoid. It's the Blu/Red wire in the top position of this connector. With ignition on, it should go on/off with the brake lights.

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/electrical/IMG_3958_zpsfi89hkye.jpg

If you have power to the solenoid and it's not engaging, then the solenoid is bad. If there is no power, then the computer or one of it's other inputs are bad. Here's a picture of the schematic to help you sort things out:

http://i8.photobucket.com/albums/a23/timsrv/TVT%20pics/electrical/IMG_3957_zpss4ahqvdp.jpg

Due to the potential safety hazards, I cannot advise you to disable the system. It would be easy to do though. In looking at the mechanism I can think of a few ways. My 86 doesn't have it and it's hard to imagine a scenario where I would ever need it. But then again, I blew a brake light fuse on my 89 once, and the shift lock not working made me aware of it............So it possibly saved me from getting rear-ended........or perhaps a fix-it ticket???

I guess if little kids or a big dog was left alone in the van it could prevent an accident (van parked on hill, e-brake not set, kid or dog knocks out of park...........:shock:.

Anyhow, let me know what you find and/or if you need anymore help. Tim

[kestrel]

excellent, tim! thanks. you really should think about going into the repair manual business. ;)