89 PA code 27

[Electric_mouse]

Finale:

Code 27 is cured. I dawned on me that if I shorted 2nd gear and 3rd gear together it would accomplish the same thing as a proper second gear switch and keep that circuit grounded for the 10 seconds required. Second gear switch would open along with third gear and not affect 4th gear as would a continually shorted 2nd gear switch. Only drove it about 3/4 mile and up to 35 kmh or so but it shifts nicely and no codes anymore.

Happy camper. So easy and here I spent a day pulling the dang thing apart and re-assembly.

[maxwedge]

Good job, most people would have given up on this, especially on an older car.

[Tech II]

I do not see how that works.....

[Electric_mouse]

Originally Posted by Tech II

I do not see how that works.....

All switches must be closed for 10 seconds after starting the engine or it will send a code. By paralleling the second and third switches it accomplishes the same thing as having a good second gear switch. Second gear switch would normally stay closed for ten seconds and open as soon as it reached that gear. Now it must wait till the vehicle reaches third gear. Since this old transmission doesn't use any signals from the ECM it doesn't affect operation. All those switches do is control fuel delivery. Doesn't really matter all that much since you're normally in fourth and OD.

This vehicle doesn't have many miles on it. It was owned by an elderly couple. Body and interior are in good condition. Two tires are new. The other two are fair. Brakes are good. It needed a little TLC like ignition switch, power ant, RH mirror broken. I can get one from wrecker here for $15. Speaker wires were broken in the left door jam. Cam sensor magnet was thrown. Cost for parts $40. The transmission had the wrong reluctor wheel for the speed sensor for this car so the speed and mileage was quite a way's off. Whoever changed the tranny didn't save the old one. I got a used one which I'll have to check for accuracy. I found they come in several different sizes. Command start is missing remotes so I'll probably install a new alarm/command. Two new in box were advertised locally on the internet for $50.

Total cost for repairs won't be much over $100.

All I have left to do is the command start if I go that way and it's ready for the road. I may pull the Oxygen sensor to have a look and wheel alignment.

Had I known more about transmissions and these codes I would have saved a day's work. But it was worth the experience.

[Tech II]

When I said, I don't see how this works, I meant the input signals to the ECM, indicating which switches are open and closed, indicating which gear the tranny is in......I know these switches are not used to shift the tranny, since this is a 4T60, not a 4T60E.....that is done hydraulically, not by the ECM....

When you start the car, all switches are normally closed.....since you have an open circuit with the 2nd gear switch circuit(either switch bad or the harness to it internally is open), by jumpering 2nd gear circuit to 3rd gear switch, yes you have removed the problem on startup....however, first gear will be ok....when you go into 2nd gear, that switch should open, and the ECM should see an open circuit, but it's not because you have jumpered this circuit to the 3rd gear circuit which is still closed.....

So, as far as the ECM is concerned, it "thinks" you have shifted from first to third to fourth......

[Electric_mouse]

Originally Posted by Tech II

When I said, I don't see how this works, I meant the input signals to the ECM, indicating which switches are open and closed, indicating which gear the tranny is in......I know these switches are not used to shift the tranny, since this is a 4T60, not a 4T60E.....that is done hydraulically, not by the ECM....

When you start the car, all switches are normally closed.....since you have an open circuit with the 2nd gear switch circuit(either switch bad or the harness to it internally is open), by jumpering 2nd gear circuit to 3rd gear switch, yes you have removed the problem on startup....however, first gear will be ok....when you go into 2nd gear, that switch should open, and the ECM should see an open circuit, but it's not because you have jumpered this circuit to the 3rd gear circuit which is still closed.....

So, as far as the ECM is concerned, it "thinks" you have shifted from first to third to fourth......

The ECM doesn't get any change signal until the vehicle shifts to 3rd. It doesn't matter. The only thing the signals are used for is fuel delivery. I pointed that out. It's minor. This transmission doesn't HAVE a second gear switch. Whatever vehicle it came from (Olds) didn't care too much about it apparently. That ECM must not have monitored second gear at all.

I don't understand your concern or argument.