High Idle on '01+ Duramax's - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 3 (permalink) Old 12-20-2005, 04:32 AM Thread Starter
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High Idle on '01+ Duramax's


1. GM part #12084913 (5 pack of terminals).

2. Toggle switch, or acceptable replacement.

3. Crimp tool, nut driver or 1/4" drive rachet/socket set.

4. 10-15' of 18 or 20-gauge wire. The OEM wire color for this circuit is LIGHT GREEN, but any color can be used.

5. Ring terminals to connect to toggle switch.

6. Fuse tap.

7. Electrical tape, wire ties, and maybe some wire loom.

8. Voltage meter

9. Good trebble light and a warm place to work.

Install Directions:

- Open hood and locate ECM. It is below and to the side of the drivers side battery. Locate the two tabs that hold the ECM cover on. There is one facing rearwards on the top, and on on the front near the bottom. There is also a wire loom holder on rear side about half way down. Remove the ECM cover, it's a tight fit, but not to hard.

- Next, your ECM will look like this:

Unclip it at the top the pry the plastic tab upward and remove the ECM. Then blow off all the extra dirt and debris so they don't get into the connectors.

- You'll need to turn the ECM so the connectors face upwards. Once that is done there are two bolts that need to be loosened to remove the connectors. Just a reminder, the connector facing the passenger side is the Blue C1 connector, the connector facing the drivers side is the Red C2 connector.

- Once the connectors are unhooked, move them aside and slide the ECM out of the engine compartment. Set it in a safe place and be sure not to hurt it. Without it the Dmax is no more.

- After the ECM is out of the way remove the plastic protector from the back of the Blue C1 connector. This will expose all of the wires and a bunch of little numbers. You'll want to find the #71 terminal.

- Get an ECM terminal (GM Part #12084913) ready and crimped on to a piece of 18 or 20ga wire. 20ga will be easier, but I used 18 with no problems. After it's crimped on the wire insert it into the #71 position on the Blue C1 connector. The #70 has a brown wire in it and the #72 is empty, so it's not to hard to find the right spot.

- It will most likely be necessary to remove the blue plastic from the terminal side of the connector. It has a clip that needs pushed in on each end to be removed. I used a small screwdriver to do this. Push the new #71 terminal in until it is even with it's new neighbors. Re-install the blue plastic over the terminals.

- Once the terminal is installed the ECM can be re-installed using the opposite of the procedure outlined above.

- The next thing will be to find a suitable place to run the wire into the cab. I used the main wiring harness boot. I slid the wire in through it.

- I then located a fuse named IGN 1 which has a 10 amp fuse in it. I installed a fuse tap with it and used it for my power source. (yellow wire in pic)

- I ran the hot wire to my toggle switch. I ran the wire from Terminal #71 to the other side of the toggle switch. The switch can be mounted in the dash or any suitable place. I chose to tie it up under the dash for now until I find it a more permanant home.

Utilization of new mod:

- On a manual truck it's wise to engage the parking brake, on my particular truck it's not necessary. The MPH must be 0, the clutch or brake can't be depressed.

- On an Allison equiped truck the tranny must be in "P" or "N". The MPH must be 0. The brake can't be depressed.

- Once all the above requirements are met you can turn on the toggle switch. When the cruise is set to "ON" the idle will increase to 850 RPM. When the cruise is "ON" and the "SET" button is pushed the speed will increase to 1200 RPM. When the Cruise is "ON" and the "RESUME" button is pushed the speed will go up to 1700 RPM.

- If the brake or clutch is depressed, or the MPH goes above 0 the high idle will kick off.

This is all based off of my '01 ZF6 equiped pickup. Others may vary slightly, but should be very similar. The LLY Duramax needs a different pin IIRC and maybe some other things to make it work. To work the pickup must be equiped with cruise control. I have a video with out sound of the high idle working. It shows the tach moving around controlled by the cruise control.


On Edit: I've been considering removing the toggle switch all together and running off of the E-brake circuit. Connect the wire from terminal 71 to the wire that's hot when the E-brake light comes on. That way the high idle can only be used when the E-brake is set. As it stands now it doesn't have to be set and if I leave the toggle switch on it won't run over 2000 RPM. That would eliminate these two problems in my case.

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post #2 of 3 (permalink) Old 08-09-2009, 09:10 PM
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anyone do this and want to sell the extra terminal plug. I don't need 5 of them
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post #3 of 3 (permalink) Old 09-11-2009, 12:13 PM
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Originally Posted by chevyhulk View Post
anyone do this and want to sell the extra terminal plug. I don't need 5 of them
When I went to buy mine I was able to just buy a single one. Post up in the wanted. There is surly someone with extras.

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