TC lock wire- Mine is grounded with key off!!!
 

This is a bit long winded. Thanks for reading!!
First the question......
On my '02 PSD, isn't the TCC wire (purple/yellow trace) supposed to ground out when the PCM sends the signal to lock the torque converter? More specificly it's the wire in the foreward GREY 16 pin connector on the driver's side wheel well that is widely used for the manual TCC lockup mod.

Now for the explanation of what I'm doing.
My torque converter fluctuates in & out of lockup cruising in O/D. So last night I went to install an LED indicator that will illuminate when the PCM sends the signal to lockup. Only the LED at this point, not a manual lockup switch, that will be next. This way I can monitor the tachometer fluctuating 300 RPM while watching the LED indicator to see if they are in sync. Anyway, I tapped into the purple/yellow wire at the fender well and ran it through the firewall into the negative of the LED. Then ran a power wire from the posative of the LED and attached it to a 12volt source that is always hot. Now the ignition was off, the keys were in my pocket LOL and the dam LED was on!!! I quickly disconnected the power wire to the LED and re-checked my wiring. Does this make sense to anyone? Shouldn't the led ONLY illuminate when the PCM locks my torque converter? I've read many write ups on this (including Guzzles) and they all say the same thing, the PCM sends the signal to lockup which grounds the purple/yellow wire.

Iv'e done a TON of troubleshooting with the tailights and trailer wiring and the brake switch (recall done) and ruled them all out as the cause of the torque converter locking issue. For now I need some advice to see if I goof'd up. Thanks FTE!!

I've never checked to see if the torque converter control solenoid control wire is grounded when the key is off. I never needed to know if it was, and I couldn't possibly care less if it was grounded when the key is off. What difference could it possibly make?

Change the power to the LED to a key on power and don't worry about what it does with the key off.

You also need a current limiting resister in series with your LED. If not you will dump a lot of current through the LED to the point where you can melt the wires.

I'm running a 10amp fuse between power and LED. The LED is a 15amp.

My point of concern is I wanted to run it by you guys to make sure I was tapping into the correct wire before I continue with the key on so I don't damage anything. It just did'nt seem right to me and I thought I had an issue. Sounds to me like it's not a big deal. Thanks guys.

A 15 amp LED? What are you using... a fog light?

:D

A fuse is not a bad idea, but even a 1A fuse is overkill for an LED. A fuse is not going to limit the current to the LED correctly. You want to put a 1k ohm resistor in series with the LED and the fuse if you want. A current limit resistor is way more important than the fuse in my opinion.

Yeah it lit up the cab like a spot light LoL. I bought a switch to do the TC lockup mod next week and it's a 15amp switch. the LED is a $3 12volt LED from radio shack.

Point taken. I'll pick up a 1K resistor tonight. Thanks for the advice.

Motorig, are you sure you want that much light in your cab when driving at night?

Do you mind posting the part number or a link of which Radio Shack LED you are running. 15 amps is a lot of light, heat, and current in a circuit spliced into your PCM and transmission. You might need a diode suppressor to keep from back feeding. LOL.

By comparison, the LED I set up for my TCC indicator is only rated for 15 MILLIAMPS, and it is plenty bright.

Ok it's not a 15 amp LED. I bought a 15amp switch for another project the same time I bought the LED and had 15amp was in my head when did the write up. The LED is in fact a 6mm LED w/red lense and a snap-in holder. Model # 276-084 bought from from Radioshack.
Here's a web link Red LED with Holder : LED Holders | RadioShack.com
The short amount of time it was illuminated last night I could see it was by no means bright but just enough to notice.

Now that makes more sense. As soon as you said "Radio Shack" I suspected you didn't have a 15 AMP LED after all, which is why I asked you for the part number. Your LED is only 15 mA, just like mine is.

You are correct about the wire color you chose Violet with Yellow strip, which is Circuit #480 that passes through Pin socket 4 of Connector C1048, that connects to Pin 54 of the PCM.

https://www.ford-trucks.com/forums/p...ctureid=151209

Awesome, thanks for the back up on this Y2K!!! So a 1K resistor is sufficient for the 15ma LED?

With 1k, it will draw 12mA. V=IR.

Sooooooo I have a funny story. I went to radio shack an hour ago to look for a resistor for my LED. As I was searching I came across an LED with a built in resistor for 4 bucks, SCORE!! I went ahead and bought a green and an orange colored, green for when the torque converter is in lockup & orange for when I've flipped the switch for manual lockup. So I'm all happy, I hop in my truck and drive away. Life is good...... LED's with built in resistors, ya! Then it happened.....I lost my torque converter. Yup, slip city. God played a mean joke on ME tonight. Luckily I was only a mile from my house. I babied it home it shifted fine other than the occasional shutter at 1-2 shift. I parked it and cried. That's my story, hope you enjoyed it.

BTW, thanks for the resistor info ebbnflow, I had forgotten about that formula.