Piggy-Back Primer

[PDQ03E]

Check My Homework!

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Ok Gurus - Please look my two charts and tell me if my planning is wrong. Here's what I'm trying to do.
I need to build a harness to piggy back 2 k-motor ECU's.
The motor will run on an '05 KTuner modified tunable ECU
The 4spd AUTO transmission will be run by the stock '03 ECU
The car is an '03 Element with a k24a2 clone motor.
I have an AEM extension harness that I will tap into as to not eff up the factory harness. The "A" and "E" harnesses are the only ones with shared functions so I will set up secondary "Pig-tails" to carry the functions to the corresponding ECU; and deleted from one not requiring input. In my chart "K"/BLUE items are Motor related. "S"/YELLOW items are Slush-box controls . "B"/GREEN items are shared by both and will be included in each pig tail.
QUESTION ONE: Harness "A"Pin 29- dose the trans need to see the TPS?
QUESTION TWO: Harness "B"Pin 15 dose the trans need to see the ELD?
QUESTION THREE: What have I overlooked as this is a whole new world to me!

[KTuner]

Nice work! I honestly can't tell you if the AT needs anything else. We've never attempted similar before.

[PDQ03E]

I feel like the adventurers heading out west in their prairie schooners! Will Share my results here .

[KTuner]

Very curious!

[PDQ03E]

Ok Guys , I've got MOTION!! My piggy back setup has a couple of kinks ;like in dash tach not working , and my in dash gear selector only showing P/R/N... but can get moderate acceleration and highway speeds. Took a 2hr ride and had 1 fault - lean on bank 1...which makes sense as it should be calibrated for the rsx injectors and I've got the element ones back in. Calling my tuner tomorrow to set up a drive!! WE"VE GOT AUTO !!!!!!!!!!!!!!!!!!!!

[KTuner]

BAM. Awesome.

[Audiophyle]

You look to be using a lot of common outputs from both ECUs, which could be causing conflicts.
In the description column on your pin outs it says what connections "drive", "detect", or "communicate" with various vehicle components. I think these are important to note because a "detects" means its an ECU input, "drives" means it is an ECU output and "communicates" means its more than just a simple voltage turning on or off.

Connector A:
Pin-20 & Pin-21 should only need to be connected to 1 ECU since it is just a power source for the two sensors.
Pin-29 I would think the TPS wire needs to be shared between ECUs. Did you notice any hesitation or delay in downshifts when leaning into the gas pedal? I would assume the tranny controller uses TPS to determine when it should down shift or up shift based on user demand, and without it the shifting response may be slower or delayed. If you think about it, the gas pedal is your only means for communicating with the ECU, how else would it know to downshift right away when you mash the gas?

Connector E:
Pin 7- You only need one ECU to drive the main relay, I would only connect it to the Ktuner ECU.
Pin 13- This may be a digital signal, splicing could be causing issues. See what happens if you unhook the S ECU from this wire.
Pin 25- This is a tach signal output, you really shouldnt have the ECUs sharing any outputs. You also didnt connect the crank shaft sensor (Connector A/Pin 7) so the S ECU has no input to generate a tach signal while the K ECU does.
Pin 31- This is an output, it should not be shared.

You can share inputs between the ECUs, but you cannot share outputs. Because of this I think its important to identify one of the ECUs as the primary & the other as a secondary.
You should have everything run through the K ECU as the primary for obvious reasons, meaning all inputs & all outputs need to run through the K ECU. (only exception is the outputs to the transmission)
The S ECU should only be connected to the outputs controlling the transmission, and share the few necessary inputs required to operate the slushbox like it should.

[KTuner]

He has a point. Definitely good info!

[PDQ03E]

Awesome help! Thanks Audiophile - I had asked these kind of questions but hadn't gotten any responses. I've begun with the tach wire already.. will test Sunday night and continue with Fix/ test cue
#1) TPS- yes shifting seems delayed. easing steadily into the throttle picked up speed well- but mashing it led to the "Bogged out groan" with no response of speed.
#2) as you can tell .. I really SHOULDN'T be playing with a soldering Iron ... the more guidance given the better we are! LOL!
#3) I have some time to work this out as the spring rush has my tuner's time locked up for a while.......

[PDQ03E]

continued brainstorming/ what I was thinking..lol.
conn "E" #7 - I wasn't sure if power source DTC memory meant only for dtc's as it seemed to be supplying the sleep mode power...
conn "E"#13+31 didn't know if trans needed to send signals for the MIL system or if they had a separated system for the gear box...
This should get positive results!