Also, one of the wires inside the transmission could be grounded. The coil will still read normally between the two pins. Besides continuity, measure each pin to ground.
If you DO find one pin grounded, you might try switching the positions of the two wires in the connector. Instead of blowing fuses, I think the solenoid will engage all the time of it is switched on the ground side.
If it is switched on the positive side, which it sounds like since it doesn't blow the fuse until it's time to activate it, it might work fine that way. Logic would dictate if there was no switching done on the ground side, they would ground it inside the transmission and just have the one wire in the electrical connector, but they might have designed it this way for some other reason.
Wrenchtech will correct me if I'm wrong, but I don't THINK any switching is done inside the transmission. If that were the case, all they'd need outside would be to apply battery voltage when the ignition switch is on. The reason for getting the Engine Computer involved is to add control for other variables. Examples would be to instantly unlock it when you tap the brake pedal in preparation for slowing down. The transmission wouldn't know that. Lockup doesn't occur when the transmission fluid is cold. The Engine Computer goes by coolant temperature. When a computer switching circuit is used, it's easy to pulse the solenoid during engagement to ease it in without a thump or clunk. Can't do that with a simple switch.
These are just things going through my mind that might help. Also, is that 20 amp fuse you're blowing in the car's fuse box or in your jumper wire? If it's in the fuse box, the computer can shut the circuit down to protect its switching circuit from damage. That type of solenoid shouldn't draw more than probably 3 - 5 amps. There are similar fail-safes for some sensor circuits on many cars. If you even momentarily short the 5 volt or 8 volts supplies to ground, the voltage will stay at 0 volts until you cycle the ignition switch off and back on to reset it, but it won't blow any fuses. It would stand to reason the lockup circuit would be protected the same way. You're bypassing that safety circuit when you use jumper wires.
Just out of curiosity, what happens if you switch the wires around when you're using jumper wires? Does the fuse still blow?
Saturday, February 25th, 2012 AT 11:25 PM