trying to finish up this harness for my car and the only thing im having trouble figuring out is what to do with the power grounds (A23, A24, B1) and the logic grounds (A26, B2). i know the power grounds tie into the tstat housing and vss etc. According to my helms it looks like the logic grounds tie into the shielding for the dist and also chassis grounds?

im just trying to figure out if i need to ground A26 and B2 or if i can leave them open. And if its cool to just splice the dist shielding into my tstat ground.

 

Generally, the logic grounds are what you would ground your dizzy shield wiring to. Grounding the shielding to chassis ground will increase the chances of picking up interference from other electronics in the car.

 

Exactly, one is clean the other is not.

 

if the ecu grounds from the tstat, and the shielding grounds to the logic ground pin, does the ecu do something that "cleans" the ground in between then?

 

Inside honda ecu's there are little honda elves cleaning the logic grounds. j/k

Honestly, I don't know. What I do know is that i've had cars misfire due to signal interference from improper grounding/shielding. Those cars also had home-made custom "tucked" wiring harnesses that looked cool, but were far from functional.

 

by improper grounding do you mean it wasnt grounded or shielded at all or was it grounded to the chassis?

 

Logic grounds are a regulated 0 volt signal for your sensors.

 

i thought that was what the sensor grounds were for? are they the same thing?

 

OEM Honda ECU's or aftermarket plug & play have (3) ground types:

Power Ground 1/2
-This is your main ground, should be to your block.

Sensor Ground
-Dedicated ground for engine sensors (MAP/TPS/IAT/ECT), transducers/potentiometers/thermistors.

Logic Ground
-Exactly as Tony said, regulated 0V ground. On B-Series, your shield grounds will be terminated to these, and branched to power ground.
-Also used as a ground for hall sensors (K-Series) and some A/T components.

At the end of the day, not a ton of manufacturers use "logic grounds", nearly all aftermarket EMS have a 0V Sensor Ground, and Power Ground. I've fooled around with different ways of tying in the logic grounds on my harnesses using S300, K-Pro, and more so with AEM (as these all use 'factory pinouts') and have had no ill effect.

 

Actually, the "logic ground" grounds the logic part of the Ecu. Without it, the Ecu will not work.

 

I have a issue with not being able to communicate to pcm through DLC. I have power at pin 16 for HDS tester. I have good ground at G451. I have 4.71 volts at E29 to 9 at the DLC. I have .017 volts on BRN/YEL off of pcm to DLC. The VSA,TPMS, SRS, gauge control mod all light up that for K line for off board communications. Is the problem sensor ground at pcm at E3? Should that be near .001 volts? The Immobilizer light keeps blinking and DLC has power and ground but no communication. The key and ignition is brand new. Obviously I cannot program the new key because I cannot connect through a scan tool. What’s the deal?

 

You need to start a new thread in an appropriate sub forum for the car you are working on, and provide more (any) information about that car. This thread is old and not really applicable to your issue.

 

did you find problem lol 4 years later....lmao but I'm haveing exact same problem exact same car and think it's logic ground in engine Bay G101. Witch lead me here lol I'll probably find out befor response lol