my 95 lost it's lockup so i installed a manual switch. it worked great. i thought it would nice to have a lit switch and found out that doesn't work so well. now it won't lockup at all, no matter what. it did have a code of 1224. tps. so i replaced the tps. [$180.00. ouch]. it did fix a weird down shift problem but not the lockup. i cleaned all grounds, and the charging system seems fine.the batteries are low i think at 12.3... i wouldn't think a little light would hurt anything. the lockup wire still has power to the switch. any ideas?

 

hopefully you didn't throw 12 volts to the converter ground that your switch is hooked to, if so likely goodby PCM. If the switch still doesn't work and you are sure that it is grounded you may have by some freak chance wrecked the overdrive solenoid. Either way 12 volts to the ground side of that system is never good.

Chris

 

all i did was replace the non light switch with a lighted switch.when i first drove it with the lit switch, i got to the end of my driveway and the truck tried to stall. then i switch it the other way. so i figured out that light on means switch is off. and it worked for about 3 miles that way then no lockup. went back to non lit switch. it has worked a few times within 500 miles of drive time. manually only. the few times it did work was just after i started driving. it stay locked till i had to shut the switch off. but lately nothing.

 

Take a close look at the trans temp sensor in the hot line and check resistance from trans to PCM and make sure the tap for the switch is a good one. Then possibly the overdrive and lockup solenoid pack in the trans.

Chris

 

this might sound silly..but one thing to look at is the brake pedal adjustment...have u been fooling around with the brake pedal in any way recently? pulling up on it?...what can happen after some time is that the pedal lever can stop making contact with the lil brake light switch...and when that happens the truck thinks the brakes are applied and ur TC will not lock even with a switch...i know this because i had issues with this after i changed my booster and had no lock-up...so get underneath there push the pedal down , pull out the lil **** and let the pedal come back...boom adjusted just like that...u never know...costs u nothing

 

sometimes with the cruise set, if i hit a bump in the road it will knock it out of cruise. i will try both of your sugjestions tomorrow. thanks guys

 

i adjusted the brake switch this morning. and it did lockup on it's own and manually. but only for about 5 miles. after braking a few times it quit working all together. pulled over to adjust the brake switch again and it wouldn't lockup again.

 

There are 3 wires at the trans connector,center is 12V power.Verify you have it with the key on,and no one touching the brake pedal.If you dont you have found your problem,if you ground both outside wires you will get OD and lockup if everything is ok inside the trans.Find out where your problem is first in the trans or the truck wiring/switches.

 

i have 12v at the connector center wire. now what? overdrive always works.