I now have a baby Girl, born August 22nd. And my '95 6.5L finally sold.

Now I will be able to order a few things for my Duramax. Among those will be an upgraded PS pump and the stuff to install this Ignition Override.

So in the next few weeks I will be installing it and will let everyone know how it turns out. I expect it will be very useful for keeping the truck warm in the winter so our little girl doesn't have to get back into a cold truck here in Northern MN. Just push a button, pull the key out, and not worry about someone stealing the truck. I wouldn't worry about it where I live, but we don't have any stores right here, and down in Duluth I would worry about someone driving away with my nice truck.

 

I would also recommend adding the high idle feature to this, so that whenever the switch is pushed it goes into high idle. It is really important not to run diesels at low idle for long periods of time.

i didnt know that.... why is this?

 

Diesels have an incomplete combustion at low idle. They basically use as little fuel as possible to keep the engine running. This causes accelerated cylinder wear as well as cylinder wash down. With cylinder wash down fuel also gets into the oil.

They came a long way when the common rail injection systems came about, especially when they started using pre-injections to quiet the idle. But they didn't solve the problem completely. In larger class 8 older trucks they would actually die if idled too long. The cylinders would get so washed down that they would not seal well enough to create combustion. Once that happened they would be almost impossible to restart unless you re-lubed the cylinders. That is why all trucks sitting overnight would bump the idle up to at least 800 rpm. It would be just enough to get a complete combustion. The newer class 8 trucks come factory with a high idle switch. Many newer ones even come with a built in automatic high idle that would raise the idle if it sat for 1 min idling.

I think there were more problems, but it's been almost 10 years since college and my memory stinks. I just remember it being very important not to let a diesel sit at low idle for long periods.

 

oh wow thanks....
ive slept in my truck many times on road trips with it idoling the entire time i was sleeping....hahaha... oops

 

Just finished installing the Ignition Override with High Idle Mod. Push the button the RPMs jump up to 800 and you can take the key out and it still runs. Press Set on the cruise control RPMs jump up to around 1250. Press Resume and RPMs jump up to 1700.

I did change how I hooked it up. I used the power feeds going to the IGN switch instead of running new wires. I also ran power to my momentary switch from one of the IGN output wires.

I attached the new Wiring Diagram along with a pic of my relays once they were all wired in, and a pic of it in action once finished and put away. You can see my button behind the shifter, no key in the ignition, and the RPMs at 1700.

Didn't take too long to install, just a lot of soldering and a roll of electrical tape.

Almost forgot, it all stops when the brake pedal is pressed. It can be used as just a high idle switch that will disable when you hit the brakes, or as an Ignition override that if the brake pedal is hit before the key is turned back on it shuts everything off.

 

I used the override a couple times yesterday, worked great. RPMs jump to 800 and I can take the key out and lock the doors. No problems. Get back in and just have to remember to put the key back in and turn it on, or it shuts off on you when you hit the brake. I remember having that problem with my wife's van when I used the remote start.

Also forgot to put what I have into it. Total install time was 3 hours. Total cost was $50 including the expensive ECM pins, $12 for 2 pins, shipping sucks for them.

 

Definitely a good write up! Ive been thinking of doing a remote start, but this seems to be the way to go. Plus i love the fact of high idle.

 

It is really actually very simple, just a bunch of slow soldering. You only have to tap into 7 wires on the truck and 6 are behind the metal plate under the steering column and the 7th is above the brake pedal. Then for the high idle you only run 1 wire under the hood and split it up to 2 ECM pins.

If you don't have an ECM terminal crimper, I would find someone who sells the terminals already crimped to a piece of wire. I've seen several on the forum who sell the terminals, cheaper than I got them for, already crimped to 4" of wire.

Let me know if you have any questions.

As for other years, I can look up the terminals for high idle easily and post them if any one is interested, otherwise I'm sure the Ign wires are the same.

 

Hey ZiGBlazer. I have a 2004 LLY Duramax. What terminals do I need to know to perform this on my model truck? Thanks

 

Ok, I did some checking.

First, manual high idle is not available for 07.5 LMM duramax's. And information is sketchy for LMM 08-newer trucks, some people say it can't be done, others say it needs to be programmed by the dealer for it to work. I'll take a look at the GM upfitter website tomorrow to find out for myself. Also the terminal part numbers are almost useless at most GM dealers, they don't have a clue what they are or how to find them. A GMC Med duty dealer or a truck body installer is a much better location to get them. I found a few people on here that attached them to a 4" piece of wire and sell them, which is nice since most people don't have the special crimper needed. I'll look for someone who sells them and post the terminal #s for each truck later.

Anyway here is the ECM terminal numbers for the different trucks.

LB7 ECM C1 connector Terminal 71. "+" on.
Terminal Part # 12084912

LLY 04-05 ECM C3 Bottom connector Terminal 6. "+" on.
Terminal Part # 15356826

LLY 06 & LBZ ECM C1 Connector Terminals 8 & 60, "+" on.
Terminal Part # 1928498135 Tray 19

There are a couple options for how to control the + power to the ECM for turning it on.

1. (My favorite) Install as part of an Ignition Override.

2. Install with a simple switch. Downside is it must be turned off to continue driving normally.

3. Install a momentary switch and a couple relays to have an auto off when the brake pedal is pushed. Just like the Ignition Override uses.

4. Hook up directly to the park brake output, so it turns on when the park brake is on.

5. Hook up to a certain brake output wire that only give a signal when the brake is hit when in park. (I have not confirmed this, it is just in other High Idle Mod instructions)

Good Luck

 

I added the Terminal part #s to the last post. I also looked up the LMM PTO info and found out what the deal is.

The LMM trucks had a much more advanced PTO option available. They used a separate PTO Control Module that took all of the inputs in and used the serial connection to the ECM to control the High Idle. So when they are installed factory it includes the PTO control module and different programs for the BCM and ECM to work with it. So it can be installed aftermarket, but it is much more involved than just adding an input to the ECM. And it was not an option for the 07.5 LMM trucks.

Have Fun,

 

what type of switch is required for this? also is there any way to change what rpm the high idle is set at?

 

I think this is a great idea even if you have remote start. If you pull up to a gas station and you're only running in for 2 minutes you don't have to turn off your truck. Checking the mail at the post office is another great example.

 

For a simple high idle, you can use any on/off switch. With the Ign Override you use a momentary push button switch. You can use the push button switch and have the brake pedal turn it off for the High Idle only but you have to use 2 relays with it.

When turned on the idle goes to 800 rpm, you press SET to bump it up to 1250, and ACCEL to bump it up to 1700. I would imagine you could change the speeds with EFI Live, but I don't know for sure.

 

ok, so if i use the diagram provided in the first post including the high idle piece. i will need a momentary switch....

 

Correct. I used the Dorman 85981 Momentary switch because it was cheap, looked good, and available at any auto parts store. It is the one in my picture on the dash behind the shifter.

I updated the diagram in the first post.

It requires fewer wires to be run underhood and is easier to hookup under the column.

 

Very nice write up. I may be dong this one to my LBZ. Is there any particular reason you added the 30 amp circuit breakers for the ignition bypass wires 142 and 342?. They are already fused at 40 amps. Not trying to pick at you. Just wondered what the thinking was.
Thanks for the very cool mod write up.

 

I would really love to do this upgrade, but I already have high idle and would like to keep that, and just do the override option without the high idle? Unless I know I'm gonna be sleeping in my pickup or away from it for a long period of time, then I"ll just flip on my high idle. any idea on how to do just the override and not the high idle, and will my high idle work if i do the override?

 

suscribed.............. good write up.

 

Excellent write-up.

 

If you do not want the high idle portion, simply do not connect the wires to the ECM terminals. It will not change the operation of the Ignition Override or any existing High Idle.

The purpose of the additional circuit breakers is for the relays. Most have a constant working load rating of 30 amps. The relays I suggested have a constant rating of 30amps and a spike rating of 40amps. So as with any electrical circuit you want the smallest rated component protected. Even though it is very unlikely that the 40amps would all go to one side, it could happen and having a circuit breaker there is simple insurance.

If you have any questions just let me know.

 

will the schematic work for an lb7 and nice write up to by the way. and thanks for the info

 

It should, except the High Idle ECM terminals. I don't have a schematic for an LB7, but those wires rarely change unless there is a major body/wiring change such as LBZ to LMM. I will try to find those diagrams.

You should check the wires to see which ones are hot at all times and which are hot when the key is on. It should be the larger 6 wires behind that metal plate under the column.

If anyone can send me the wiring diagrams for the LB7 or LLY I would be happy to take a look and make another diagram for those engines to make it easier. I already have access to the connector end views through GM upfitter.

 

Seriously amazing write up! Helluva lot of intellectual property in these posts for sure! lol nice work.

 

This is interesting im probably gonna do it to my truck this weekend