Ignition switch replacement

TimL · #1 10-17-2006, 01:35 PM

I've got the symptoms of a faulty ignition switch on a '97 silverado. Can someone please tell me whether or not I will have to take it to the dealer to reprogram the computer if I replace it? The dash seems to lose power & it gives the codes P0740, P0785, P1860, then seems to be stuck in 3rd gear. I erase the codes & it's fine, for a while. Any help would be greatly appreciated.

2000CAYukon · #2 10-17-2006, 05:13 PM

No reprogramming should be required for an ignition switch replacment.

//2000CAYukon

777stickman · #3 10-17-2006, 06:08 PM

All of those codes are tranny related.

P0740=TCC Enable Solenoid Circuit Electrical.
P0785= 3-2 Shift Solenoid Circiut Electrical.
P1860=TCC PWM(Pulse Width Modulation) Solenoid Circuit Electrical.

1st most common thing in all 3 of these codes, besides the ign sw, is the TRANS fuse. It's located in the IP fuse block #20 10a. Don't check it just swap it out with a NEW one.

Try it and post back.........Steve

locknkey · #4 10-18-2006, 12:13 AM

Its not an Ignition key switch issue, Problems would consist of not being able to turn ignition key smoothly in any position, stuck key, bent key (Could be cut to replace... or broken key, could be remove if no one has tried to remove it previously. IF it would not start and the thief light will blink, Fuel pumps shut down) to replace it will have to be programmed on-board with new switch and key, door/hatch locks could be rekeyed to match ignition key.
Sound like its going to be a transmission problem.

JaVeRo · #5 10-18-2006, 12:39 AM

I had a 95 Suburban company truck that lost third gear. I could stop and kill the motor, crank it back up and everything worked fine. After doing this 4-5 times in two weeks I finally took it to the shop. It was the ignition switch.

James

2000CAYukon · #6 10-18-2006, 12:49 PM

Quote:

Originally Posted by locknkey

Its not an Ignition key switch issue, Problems would consist of not being able to turn ignition key smoothly in any position, stuck key, bent key (Could be cut to replace... or broken key, could be remove if no one has tried to remove it previously. IF it would not start and the thief light will blink, Fuel pumps shut down) to replace it will have to be programmed on-board with new switch and key, door/hatch locks could be rekeyed to match ignition key.
Sound like its going to be a transmission problem.

locknkey,
The issue is not with the lock and tumbler/cylinder. The issue is with the ignition switch which is an electrical device. Here is a picture of the one for my truck (90 GMC K1500) http://198.208.187.182/internet/View...tNumber=D1405B

When this switch goes bad, it does not provide the correct voltage to the transmission and the transmission does not operate correctly.

This can be tested by checking the voltage at the transmission harness. This is also a fairly common problem.

//2000CAYukon

TimL · #7 10-18-2006, 03:08 PM

With the tranny codes always being in conjunction with the dash power problem, I took a leap of faith & picked up a switch, it's the whole harness. Of course I didn't have the inverted torx socket required, but found one today. I'm going to try it tonight, the new one is missing 2 wires that go to the ignition cylinder, that's kinda got me worried about security problems, but I'm not yet sure those two wires are truly part of the ignition switch. I will post back what I find, thanks for all the replies. BTW, I'm also replacing the #20 10A fuse.

TimL · #8 10-24-2006, 12:43 PM

The plug I was worried about actually had 3 wires, red/wht, orange/blk, and blue, and it did go into the big plug that is under the dash. I transferred it from the old harness to the new harness, and had no problem with security. I don't know if I had to or not, but I was afraid not to. On the big plug that goes under the dash, remove the blue clips on either end, then push the retaining clip down from the connection side with a small screwdriver, I used an eyeglass screwdriver, then just pull the wire out. The truck is running & shifting fine. Message boards are the greatest, maybe somebody will google this thread someday and be helped like I was. Thanks!

777stickman · #9 10-24-2006, 05:55 PM

The truck is running & shifting fine. Message boards are the greatest, maybe somebody will google this thread someday and be helped like I was. Thanks!

TimL: Great job and thanks for the post back.

dpriceis · #10 12-31-2006, 08:14 PM

Hey I've got a 2000 with the same problems, How hard was it to change and how much? And did it fix it?

Thanks,

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