Engine Dies In Anything But Park 4l80E

[Hambone!]

Got a good prob here if anyone can shed some light on it. Not really a Pro-Touring vehicle, but after reading several sites, you guys are much more technical than the truck forums. Have a 2000 Sierra with a supercharged LS3 (Thx to Travis) and a 4L80E trans. Starts and revs ok, but ign goes away as soon as I take it out of Park. Rev it up, shift, slam it back into Park, and the engine will catch itself and run. Occasionally the shift indicator shows "2", mostly it follows the position of the shifter. My scanner also shows the feedback from the trans, and while the shifter is in Park, the trans reports "2".....sometimes "1" when revved in Park. Nothing else happens, no loading of the engine, no noises, clunks, vibrations...nothing. The PRNDL switch is new, which incorporates the Neutral Safety switch. Any ideas?

[Nessumsar]

Are you sure you are loosing ignition? Seems to me that the convertor isn't slipping. Can you roll the car back and forth with it in gear? Sounds like a dead/locked up convertor.

The Neutral Safety switch only interupts power to the starter, it shouldn't affect ignition. Correct me if I'm wrong guys...

[Hambone!]

Are you sure you are loosing ignition? Seems to me that the convertor isn't slipping. Can you roll the car back and forth with it in gear? Sounds like a dead/locked up convertor.

The Neutral Safety switch only interupts power to the starter, it shouldn't affect ignition. Correct me if I'm wrong guys...

Tach instantly drops to zero, so possibly there is a power interruption, but scanner doesn't lose communication and all the other parameters continue streaming. Converter is new, so its an unknown, but a dead/locked converter would at least load the engine. Neut switch is part of PRNDL switch which provides signals to the PCM. Old one looked like hell and had "Lucas" on the side, so replaced it. No change.

[kmdracer]

Sounds like a column wiring issue to me. Sorry I can't narrow it down more for ya.

[Hambone!]

With the PRNDL switch plugged in but not attached to the trans, the engine quits when I rotate the wheel.

[kmdracer]

Again, this sounds like a column issue. I haven't been into a column on a newer GM truck yet, nor do I have a wiring schematic for it. It sounds as if you are loosing the ignition signal from your key switch. I'm more familiar at the moment with the newer Dodge columns. They have what Dodge calls a "Multi-switch" that everything in the column goes through (as well as a few things you wouldn't think should be there) I had a problem where sometimes the Air Con Blower would juts shut off. Took me a month or two to figure it out It was the multi switch in the column.

Don't know if you have schematics for your truck or not, but if you don't Autozone has quite a few. Gave it a quick look, and they do have your truck listed. To get to the wiring diagrams, you will have to register, input vehicle data, click on "repair info" then click on "vehicle repair guides" then "wiring diagrams"


After re reading your original post, I see your struck is not stock. How long ago did this problem start happening? What was the last thing done to/with the truck before the problem started?

[Hambone!]

I meant the wheel in the PRNDL switch, the one the shift shaft would normally rotate. I guess it sounded like I meant the steering wheel. My bad. I have seen what you're describing, but with the switch plugged in and dangling, I can move the shifter and spin the steering wheel with no effect. I wish it were something in the column, this one is a lot easier than the old-schools tilts I used to take apart just to tighten those 4 damn bolts. (ugh) The problem was discovered the first time the tuning shop tried to shift it out of park. I never started the engine myself, since I didn't have the right throttle body. The called me up to tell me about this problem. I did change the engine to an LS3 with a TVS1900, but the only electrical "trickery" was adding the Lingenfelter box (TRG-002 I think). Running the original 2000 computer and harness. The only change to the trans was a new converter. Its the same trans that has served me well for years. Is it possible I pinched or cut something? Sure. It's just that nobody can give me any insight based on the symptoms and what the scanner tells me. If there were an input missing a signal, I'd be able to trace it out, if a wire were cut, wouldn't a fuse blow, or prevent me from talking to the trans computer? Its a real pisser. At least now I got it towed back to my place so I can work on it. It may have nothing to do with the trans at all, its just the only thing that didn't check out initially. (Reporting 2nd while in P) Ideas welcome.

[kmdracer]

Ah, I get you now..sorry to try and lead you down the wrong path. So, with the switch plugged in, but not mounted in place, you mean that it is plugged into the column harness, and the engine stays running, right?
If so, since the switch is new, I'm kinda clueless on this one. Perhaps if I was there in person. Good luck to ya now that you've got it back so you can work on it personally.

[Nessumsar]

I'm still thinking it is a bad convertor. Maybe when they put the trans back in they cut/chaffed the wire that controls the lock-up function? I'm not sure how those transmission lock-up (under open or closed circuit), but a cut or grounded wire could produce either of those.

[Hambone!]

Thx kmd..... I'll just have to attack it 1 circuit at a time right now.... Yes, at least I have it back and can dig in.

[Hambone!]

I'm still thinking it is a bad convertor. Maybe when they put the trans back in they cut/chaffed the wire that controls the lock-up function? I'm not sure how those transmission lock-up (under open or closed circuit), but a cut or grounded wire could produce either of those.

Well it's certainly possible a wire was cut, or smashed/shorted to another one, I mean things happen... But even with the round 15 or so pin connector unplugged it still dies. But wouldn't a bad converter always be a load on the engine? Or at least while in any gear? This things just switches dead off. No struggling, no lurching, not like stalling in a stick shift car, its just so damn strange. Also, the tach drops to zero, like power is being cut, as if it were a column issue, but I can duplicate the symptom from underneath just by spinning the wheel in the PRNDL switch. Maybe I should call a priest. LOL

[SicMonte]

we need to get some input from Bowler or some trans company here.......anyone??

[Hambone!]

Well, talked to the folks at Bowler, and even though they had nothing to do with this problem, they're still trying to help. There is however, some new information. It seems the trans DOES try to engage, if only for a second as the engine is slowing down. Also, the Ign1 Relay cycles and the fuel pump primes each time the shifter comes back to Park. Oddly, no fuses are blown and none drop out when the engine dies. Very strange. Been looking for a GM Tech Line to call, so far the dealers have been no help.

[12sec ss]

Well, talked to the folks at Bowler, and even though they had nothing to do with this problem, they're still trying to help. There is however, some new information. It seems the trans DOES try to engage, if only for a second as the engine is slowing down. Also, the Ign1 Relay cycles and the fuel pump primes each time the shifter comes back to Park. Oddly, no fuses are blown and none drop out when the engine dies. Very strange. Been looking for a GM Tech Line to call, so far the dealers have been no help.

To me its strange why ign1 relay would cycle when shifter is moved, i would track that down first if it was my car

[Hambone!]

Not quite sure how it did it, but it was a Lingenfelter module causing me all this trouble. It was waaay sensitive, and didn't like where it was tapped into power. Looks like this thread is closed.