tranny change now won't start

1999 Buick Park Ave 3.8L plane Jane, non supercharged 160K mileage

Rewind to 4 months ago, car came home and at highway speed it suddenly felt like it was in neutral and wouldn't go any longer. Checked fluid, level was good, but fluid looked bubbly and slightly burnt dark red. Linkage was intact and no obvious cause. Had it checked and confirmed the tranny or the torque converter was shot. Obtained a used tranny from a like PA with 90K from a junkyard, which the tag said tested/good. I think it was also a 99 plane Jane like this one.

Fast forward to today. Tranny was installed and now car won't start. :banghead: Turn the key to the ON position, all dash lights, DRL's etc illuminate as normal. Turn key past to RUN position and all dash lights go off and car does nothing. The PRND21 lights up, but it will not show that it is in PARK and will not indicate another gear when shifted. Car is able to be started and run by crossing terminals. Battery is weak, but had it on the charger while doing checks.

It appears that there is a miscommunication somewhere regarding the tranny or possibly the theft alarm/pass key/security it has. Resetting the computer with a Snap On scan tool has little effect. One code was B0802 brake to Shift Indicator Short Ground. It seems like either the tranny is not being recognized or there is a safety feature that is disabling the vehicle from being started. Or the guts behind the top plug on the used tranny, which I assume is the neutral safety switch and other electronics, has an issue. But going back to the above, it had apparently tested good.

I'd like to know if anyone else has experienced difficulty replacing trannys with regards to this. I've never had an issue with unhooking the battery and having to reset any vehicle theft software. There were no issues with the vehicle before and it was maintained and ran like a top. Thanks for your ideas.

Don't forget the ground wire from the Eng/Tran to the fire wall!

Don't forget the ground wire from the Eng/Tran to the fire wall!

Thanks for responding Dan. The car is at my friend's garage. He's able, but let's hope he didn't forget that.

And the trans prndl sensor connector on top of the trans where the linkage goes into the unit.

And the trans prndl sensor connector on top of the trans where the linkage goes into the unit.

All plugs were put back in their original spots on the used tranny. If you refer to the plug right on top of the trans, in which behind it in the tranny is the electronicsa and guts of the whole PRNDL and neutral safety etc, it's a big plug about 2 inches in diameter. We had that plug in and out to check for a loose connection, short or otherwise, but nothing seems awry.

It's a real thinker. I'm going to try another master key spare that I have, but don't think that will do anything. I don't see why the key we have in the car would be bad or maladjusted. It's worked well for years. But it certainly seems like something vehicle theft related or the used tranny has an issue with the electronics behind the plug you refer to. The real problem I am having is trying to pinpoint and identify what is going on. Right now we're just kicking the tires wondering what to do next.

I appreciate the ideas guys, keep em coming. Every angle needs to be looked at.

Did you use the P/N safety switch from the original trans? If not, replace it and see what happens. I have seen these switches damaged during removal, or simply go bad sitting in a JY for extended periods.

We can assume ther is no current to the starter solenoid, and the dash security light is off?

Did you use the P/N safety switch from the original trans? If not, replace it and see what happens. I have seen these switches damaged during removal, or simply go bad sitting in a JY for extended periods.

No, the used tranny bought was unaltered. They said it tested good, but does that mean they tested the safety switch good or just the mechanical function of the trans.....

We can assume ther is no current to the starter solenoid, and the dash security light is off?

I'd assume that since the starter doesn't operate Max. Starter is mechanically good. As for the dash secirity light, I'll have to check that later.

When the car was driven regularly, the security light would sometimes be on, on the dash and sometimes be off. It depended on how we started the car, either with the remote start or with the key.

No dash security light. I really think this IS probably an issue with the neutral safety/trans switch, which is buried internally. Problem is, on this particular transmission, it means taking the whole side cover off of the tranny to replace the assembly. There isn't much room and it is a very tight fit. My friend is thinking along the same lines, but not thrilled at the thought of disassembling the tranny. The older cars used to be so easy, an assembly right on top, easily changed. Not so anymore.

We have had a number of guys simply get the wiring schematics for the newer style and older style P/N switch and install the older style and wire it in to avoid having to tear the trans apart.. The threaded bolt bosses and the shaft are still set up for the older switch even on the transmissions with the internal switch... Look close at your trans, right at the shift select cable on top of the trans...

I would go this route as opposed to tearing the trans apart..

I wonder if before the whole tranny removal started, if the seafoam trick would've done anything. Probably not.

The only diagram I could find of the tranny sensors, doesn't show what is behind the top, very top of tranny, plug/harness, which I assume is the neutral safety switch. Further back on the lower top of the tranny is where the trans shift linkage is. Does anyone have a diagram of what/where the Neutral safety switch is, what it looks like.

What I am not 100% sure of is the year GM changed over to the Internal trans range switch... I know in some models this was done for the 2000 model year.. But you should be able to make wither one work...

Do you have your old Transmission? And did it have the wires running into the trans like the unit you replaced it with?

As well what did the Trans come out of?

What I am not 100% sure of is the year GM changed over to the Internal trans range switch... I know in some models this was done for the 2000 model year.. But you should be able to make wither one work...

Do you have your old Transmission? And did it have the wires running into the trans like the unit you replaced it with?

As well what did the Trans come out of?


Our 99 is internal. The used tranny is identical. Honestly rather than splice wiring, it needs to be done per the book. It's a wife vehicle for work and work travel. I'm kicking myself now for going the route I did. Hindsight is 20/20.

i'd tale starter off and if you can leave wires hooked up and turn key and see if it kicks out a spins. first alway's undo your neg. cable until you take starter loose.

i'd tale starter off and if you can leave wires hooked up and turn key and see if it kicks out a spins. first alway's undo your neg. cable until you take starter loose.


Thanks for the reply Scrapper, but the starter is verified good. The issue is undoubtedly with the used installed tranny. Either something is not hooked right or the neutral sensor electronics in the used tranny are not up to snuff.

What I'd give to know for sure. 4+ months and counting on this should've been basic R&R.

One thing that seemed slightly different to me. When I got in and tried to start it, the shifter wasn't quite as smooth as it always has been before. I don't want to say it is binding, but the shifter used to almost glide through the gears manually form P to R to N and so on. Now it feels like there is a slight bit of unfluidness. Makes me wonder if it was put in correctly down below on the tranny. Although on the tranny, it is just a pivot post that holds the trans range shifter cable. So not sure about that.

Thanks for the reply Scrapper, but the starter is verified good. The issue is undoubtedly with the used installed tranny. Either something is not hooked right or the neutral sensor electronics in the used tranny are not up to snuff.

What I'd give to know for sure. 4+ months and counting on this should've been basic R&R.

One thing that seemed slightly different to me. When I got in and tried to start it, the shifter wasn't quite as smooth as it always has been before. I don't want to say it is binding, but the shifter used to almost glide through the gears manually form P to R to N and so on. Now it feels like there is a slight bit of unfluidness. Makes me wonder if it was put in correctly down below on the tranny. Although on the tranny, it is just a pivot post that holds the trans range shifter cable. So not sure about that.

can you unhook neutrual safety switch and hold it in gear while you trieing to start it?

We had the top plug (neutral safety switch electronics) unplugged, but not sure if we tried starting it like that.

We had the top plug (neutral safety switch electronics) unplugged, but not sure if we tried starting it like that.

i'd try it but before you get drunk...lol...