E-brake ECM grounded - surprising results

[Tinman]

On a previous thread, I mentioned how I'd like to keep the TC locked in O/D off mode. It was suggested to ground out the E-brake connections on the ecm to accomplish this. Well, after many tries, I finally got it done. (I had some problems getting the right connector for the ECM pins and getting them to work properly. Serveral errors on my part made it more difficult than needed. It's really quite easy. ) I got the ECM pins from BD and soldered them to some 18 gauge wire and grounded out pin 39 and 42 to the battery. I'm not sure both are needed, but that's the way it is now.



I got the desired result as the TC stays locked now to 25 mph in O/D off. Can't tell you how much of an improvement this is. I drive in O/D off a lot and this is so much better. Also, it is in tow/haul all the time now. What I didn't expect was the cool way the ECM bumps the throttle when it shifts from 4th to 3rd on deceleration. Kinda like double clutching. It makes the 4-3 shift with the TC locked very smooth. (In the non-grounded tow/haul mode, it would unlock the TC, shift to 3rd, then re-lock the TC, no throttle bump. ) Overall, this little mod. is one of the best things I've done to the truck. Much more pleasurable to drive. I highly recommend this to anyone with an auto. Thanks guys!

 

[JCleary]

Yeah, I drive with the E-brake on all the time because of how much better the trans acts...

 

[SKneeland]

??, this is on your 06? you mean EXHAUST brake or EMERGENCY brake?



i retested mine after reading your post the first time this morning. in OD off mode my TC locks up at about 40mph.

 

[JCleary]

Exhaust brake.



It will make your TC lock at 30, and stay locked down to 22mph.

 

[BHolm]

HA! With my six speed, I can run with the brake on as slow as I want. I had the brake on my '06 Mega auto, loved it but I have to admit, it works a whole lot better with the manual. The mountain pass I frequent has a 25 mph limit on it and I can run the brake a whole lot more with the six speed.



Sounds like a cool mod though! Almost as good as having the manual trans

 

[RRees]

On my truck (no exhaust brake), on Tow/Haul it keeps the TC locked until 22mph also.

 

[Tinman]

On my truck (no exhaust brake), on Tow/Haul it keeps the TC locked until 22mph also.

Yes, in tow/haul the TC stays locked. What I wanted was the same thing in O/D off. Driving in town or mountain roads you don't need 4th gear. Many times you get up to OD shift point just to slow down again. Without the E-brake ground, the TC unlocks at about 50mph or something stupid. With the ground in place, O/D off behaves like tow/haul except without 4th gear. Like I said, the other thing was the way the engine rpms bump to smooth the 4-3 shift. Also, I didn't mention was that the TC locks sooner on accerlation, like in tow/haul.

HA! With my six speed, I can run with the brake on as slow as I want. I had the brake on my '06 Mega auto, loved it but I have to admit, it works a whole lot better with the manual. The mountain pass I frequent has a 25 mph limit on it and I can run the brake a whole lot more with the six speed.

Yeah, yeah. You guys with the manuals have it easy. Buy and drive it. A good auto is second to none, but the problem is the factory auto is far from good. This little $5 mod. helps a lot. It will have to do until I get DTT'd.

??, this is on your 06?

Sorry, it's the '06. The earlier trucks don't have e-brake ECM contections. That's the reason for the transmission controllers from the transmission vendors. This works much better than the Shift Controller from DTT on the '01

 

[Matt400]

Well, after many tries, I finally got it done.

I got the desired result as the TC stays locked now to 25 mph in O/D off.

Does this give you locked shifts 2-3 and 3-2?

 

[Tinman]

No, it shifts 2-3 as usual. If the selector is in 2nd it will lock, then unlock to change to 3rd if the gear selector is moved to drive. I think it does go from 3-2 locked, I haven't paid much attention. But it's the same as the regular T/H mode in regards to 2-3 and 3-2.



Since I first posted, I put a switch on the dash to control this circuit. Works well. Nice to easily be able to put back to stock if you go to the dealer because of the soft code. Turn if off, clear the code and the dealer will never know. It would really have them wondering how a e-brake code comes up on a truck without and e-brake. Oh, and pin 39 is all that is needed. I disconnected pin 42 and it still works.

 

[Matt400]

Interesting, wonder what that pin 39 would do for an 05. .