LS3 ECU Wiring Harness - Page 4

Jethrow · #61 (**permalink**) 06-05-2013, 09:17 AM

Hi sideshow.
The lead I use from battery to starter is what was supplied in the FFR kit and is designed for boot mount batteries. I actually mounted my battery to the front as it can sit lower there and to move some weight forward a bit.
I do not know its true size but it is a round insulated cable with a diameter over the insulation of 9.4mm. Looking at your chart it is then maybe 1 or 0 AWG?

Jethrow · #62 (**permalink**) 02-02-2014, 07:44 AM

OK, next saga in my wiring quest.

Got some trouble getting the GMPP LSx ECU talking to my Speedhut speedo. For all you LSx bandits out there, where did you pull your vehicle speed signal from, and did you have to mod it before putting it into your gauge?

Currently I am taking my signal from the 'bulkhead connector, position D' and have tried

a) wiring it direct to the speedo (no luck)
and
b) wiring it direct plus adding a 12V power source thru a 10000 ohm resistor (also no luck)

Any thoughts welcome.

Tim

sambo · #63 (**permalink**) 02-02-2014, 06:07 PM

Tim, my L98 computer (E38) is wired to the Vehicle Speed Sensor on the side of the T56. Straight from computer to gauge with no resistors.

Jethrow · #64 (**permalink**) 02-02-2014, 08:03 PM

Quote:

Originally Posted by sambo

Tim, my L98 computer (E38) is wired to the Vehicle Speed Sensor on the side of the T56. Straight from computer to gauge with no resistors.

Thx Sambo,

Is your straight from computer to gauge via the bulkhead connector? And do you also have a ground wire from the gauge as well?

Jethrow · #65 (**permalink**) 02-04-2014, 06:59 AM

So I have been doing some testing, and by using a OBDII reader I can see that the speed sensor in the gbox is reporting a signal to the ECU. So the issue is either I have an incompatible signal coming out of the ECU bulkhead connector (or no signal - can I test this?) or a faulty gauge.

Not sure where I will go next?

sambo · #66 (**permalink**) 02-04-2014, 07:09 PM

Quote:

Originally Posted by Jethrow

Is your straight from computer to gauge via the bulkhead connector? And do you also have a ground wire from the gauge as well?

I don't have a bulkhead connector as the computer is inside the cabin, but yes the speedo signal runs straight from computer to gauge. All gauges need a ground in order to function, otherwise there's no circuit.

Jethrow · #67 (**permalink**) 02-09-2014, 08:04 PM

OK - got it going now! YAY.

So a trap for the younger players. Turns out it was always working. Thing is for these gauges (Speedhut) the speedos read zero until you do a calibration. Then they start reading (showing) something.

So I did a dummy calibration to test, and now it appears to work fine. I will recailibrate when it is driving.

Glad is resolved but this caused me a few headaches till I figured that out.

Modena · #68 (**permalink**) 02-09-2014, 08:44 PM

Serves you right for not RTFM.

Glad you got it going.

Zedn · #69 (**permalink**) 02-10-2014, 01:32 AM

Tim, did you need to add the 12+ pull-up for your speed hut tachometer?

Jethrow · #70 (**permalink**) 02-10-2014, 07:04 AM

Hi Zedn,
yes, I needed the 12V pull-up on both speedo and tacho. I will be honest and say I do not understand exactly what that does to help, but I wired per the instructions and they both work.

The manual is not real clear on the zero reading for the speedo until calibration. (Actually it does not say that at all.) The tacho worked right off, but I did have to select the correct pulse/rev for it to read right. It still read however before I did the selection.