Diesel Place banner

1 - 20 of 30 Posts

·
Registered
Joined
·
412 Posts
As promised here are step by step instructions with pics for future reference. Also I want to make sure and mention here that this mod is only supposed to work on ODB1 trucks. And a big Thanks to Jifaire for the information he supplied to get this accomplished.

I came across this rocker switch on some equipment we were throwing away at work so the price was right. It's what is referred to as a "single pole double throw" or SPDT switch. The center pin is connected to one of the outer pins depending on what position the switch is in.





Here is the switch mounted in the dash plate above the cargo lamp switch. All I had to do was cut a 1/2 inch by 1/2 inch hole with my dremel tool and stick it in. It was a little loose so a little hot glue helped that out.





This is a picture of the wiring harness I soldered up. I just brought the ground out of the piece of yellow heat shrink since it is just going down right below the switch to tie to a ground. The other two leads I put in black heat shrink and headed toward the PCM behind the glove box.





This picture shows where I tied the ground down. This is connected to one of the outer pins on the rocker switch.





To remove the glove box first release the left side catch that keeps it from opening too far.





Next pull in on the right side corner of the glove box till it clears the dash and comes loose.





This diagram shows the pinout of the front Blue PCM connector that is closest to the firewall. The row that is designated C is the bottom row of this 32 pin connector.





This picture shows the PCM as it sits in the dash, the blue connector is in the very back so I just pulled the PCM out to get to it. I disconnected the cable connectors as I could get to them on the way out.





This picture shows the splice I made. The wire that goes away from the PCM with the blue heat shrink on it is the wire connected to the center pin of the rocker switch. The wire going into the PCM connector is connected to the outer pin of the rocker switch opposite of the ground. I soldered the wires to make sure they are good connections and then used heat shrink to insulate them.





Here is a better look at the blue connector going into the PCM. The picture looks like the brown wire is to the left of the red but it isn't. The red wire is on C10 and the brown wire is on C11. Also in the diagram above, it says C11 has a tan/blk wire, I couldn't see any black stripe on mine it just looked brown to me. The wires on my C1 and C2 were different colors as well but most of the other wire colors matched up with the chart above.





Once the connections were complete I taped it up to protect the wires.





Here is a picture of the finished dash switch. I'll probably add a label on top for "TCC Normal" and one on bottom for "Locked". I picked this dash location because it seemed like the best with the shifter in gear driving down the road.

 
  • Like
Reactions: Iraqvet

·
Registered
Joined
·
453 Posts
Excelent! This mod has now been bumped up to a higher position on my list!

Mods, how about adding this one to the FAQ?
 

·
Registered
Joined
·
907 Posts
looks like a FAQ to me! nice work:)
 

·
Registered
Joined
·
471 Posts
I need a "mod fix" as I haven't done one lately and $$$ are short right now so I need a cheap mod so this is it. In cab TCC lock mod.
 

·
Registered
Joined
·
538 Posts
nice instructions fonecop! really appreciate the show-and-tell. Thanks for going through the trouble.
 

·
Registered
Joined
·
412 Posts
Discussion Starter #8
You're welcome. This job was condusive to taking my time and taking pics along the way. Plus this one looked like uncharted waters as far as connecting it inside the cab so I thought I'd try to save someone else a little time. This site has helped me so much it's unbelievable.
 

·
Registered
Joined
·
471 Posts
Hi, just in the middle of this mod and had a question. In the link to the chart it has normal voltage for C11 key on as B+ which is battery voltage and .4 volts with engine operating. Now if the switch was left in the lock position would this not be putting battery voltage direct to ground when the key is turned on but engine not running yet? Now because this voltage has gone thru a load (soleniod or something) does this make it OK for that to happen?


http://www.dieselplace.com/forum/garageimage.php?do=full&p=38448
 

·
Registered
Joined
·
9,366 Posts
The voltage load comes from the tranny side... the PCM is responsible for grounding that end of the circuit only. When you interrupt the line (C11) with the switch, you are effectively isolating the PCM... in effect, line C11 is no longer hooked up to anything.

The switch then grounds the wire coming up from the TCC solenoid.

What I'm saying is, it doesn't matter what the line voltage was... you cannot hurt the PCM by doing this mod.
 

·
Banned
Joined
·
628 Posts
i,m right in the middle of this and my blue connector is wired different, my C11 has a blue wire in it, the solid brown wire is in D8,.. the only tan and black wire i can see is in a pink connector,.*sigh*
Nick
 

·
Registered
Joined
·
6,945 Posts
If you pull that latching tab off the connector, the wire positions can be clearly seen

10 red is correct, as is 12 blank, so use the 11 blue wire for the connection.

13 is yel\blk

14 is ltgrn

15 is blank w\o EGR

16 is dkblu\wht
 

·
Registered
Joined
·
9,366 Posts
I'd have to agree with JD, phantom. I did my splice doen by the tranny, not inside the dash, but my wire was blue or purple, not brown too. Mine is also a 94... maybe that matters?

It did, however, go into connector pin 'S' on the side of the tranny, so I hooked it up and it worked.
 

·
Registered
Joined
·
471 Posts
One thing you can do that might verify, once you cut the wire there should be battery voltage from the tranny side with key on and .4 volts running.
 

·
Banned
Joined
·
628 Posts
TA DAAAH!!! works great,. really holds second gear for the times when you want to be silly,..:D
thanks gmctd
Nick
growing old is mandatory, growing up is optional,.
 

Attachments

·
Registered
Joined
·
6,945 Posts
Or pull the trans connector, see what color is on pin S - should be same as pin E11 at the Blue 32-pin PCM connector

BTW - that attached print is incorrect - to prevent confusion, connector configuration is as follows

Pink 24-pin is lettered A-B

Pink 32-pin is lettered C-D

Blue 32-pin is lettered E-F, tho it may be physically labled otherwise
 

·
Registered
Joined
·
481 Posts
Just did this to my truck tonight and it was super easy to do. It is nice to be able to tell the TCC when it needs to stay locked and quit wasting fuel by turning it into heat. I think I will really see the benefits when I use it to tow.
 
1 - 20 of 30 Posts
Top