Hi All;

I hope this is the right place for this post. Although I've done a lot of work on gen IV powered corvettes, this is my first LS-swap.

I'm putting a 2008 Corvette LS3 into a 1963 Corvette. I have no BCM or TCM ... as I'm using a Tremec 5-speed. I'm in the process of wiring up the fuse box in the DIY harness I put together from the original Corvette C6 harness that came with the drop-out. I'm having some difficulty getting clear info on what the ECU action is on the following pins. I want to get this right to avoid blowing the ECU up when I get to the initial power-up stage that I need to get to to run HPtuner on the ECU-cleanup.

1/ fuel pump control: when the ECU turns the pump on, does the ECU apply +12V to this pin? ... or is it grounded by the ECU when the ECU activates the pump?
2/ Fan control: same question as for the fuel pump control
3/ MIL: when the ECU activates "Check engine light" ... does it apply +12V? or does it ground this pin?
4/ for the GM high speed LAN connections from the ECU to the ODB connector ... do I need to do anything special with these? I've read here and there that a 160ohm resistor needs to soldered between the +ve and -ve GM HigHSpeed LAN lines ... .for impedance matching reasons.
5/ On my engine there is an oil level sensor in the passenger side of the oil pan. There are three wires on the connector. what are the 3 wires? and which ones do I need to retain for the ECU to "happy". I wouldnt mind if a low oil level condition causes a MIL-light-on condition .... but its not a "mandatory" thing.
6/ my 1963 ignition switch "start" position (+12v when the key in the "engine-start" position) will go to two places ... the first is the starter solenoid ...and the second is the ECU pin 19.
7/ my ignition switch "run" position (+12v when the key is in the engine-run position) will activate a relay which powers the various engine functions (mostly pink wires in the LS3 harness) and also o pin 47 on the ECU

Comments/help much appreciated!

Thanks
Erik

 

The fuel pump gets 12+ the fan relay gets a ground as does the MIL from the ECU, unless you plan on using the LAN for anything I'd ignore it, I'm not sure what the oil level sensor does, I ignores it on mine and bought a plug for the hole in the oil pan, it looks like you have the ign switch covered.
You should be good to go.

 

Hi 79LS1FOX;

Thanks for this info. I went ahead and powered up my whole setup. The good news is that nothing catastrophic happened .

I wired the OBD port up as follows;

Pin 16: + 12V key-run (aka key "hot")
Pin 4 & 5: chassis ground
Pin 6: HS CAN +ve (connected to E38 ECU pin 28)
Pin 14: HS CAN -ve (connected to E38 ECU pin 27)

You have to also connect the E38 ECU pin 18 ... "Serial Data Wake" to +12v key-run .... or the HS CAN wont do any communicating (Brendon on www.lt1swap.com mentions this in his LS3 info).

Managed to get the ECU talking on the CAN OBD connection ... so now I need to finish powering everything up and see what codes I have left to fix ... or delete.

Cheers
eboch

 

The C6 Corvette had a fan controller that needs a PWM- signal from the ECU. Unless you changed something, that is how that fan pin is configured. I suggest you keep it that way and get a C6 fan controller. Having a variable speed fan reduces the strain on the electrical system when the fan kicks on.

Andrew

 

eboch
Pin 16: HS CAN +ve (connected to E38 ECU pin 28) is this a mis type 16 should be 6 ?

 

79LS1FOX;

Good eye! ... yes my typo/mistake. HS CAN +ve (connected to E38 ECU pin 28) is connected to the OBD connector pin 6. (note: I editted the original post to fix this error ..)

Cheers
eboch

 

Hi Project GatTagO;

I did think about this, but I ended up using an aftermarket rad/fan setup (single fan) which only has a fan on/off control. The rad space & opening in a C2 corvette arent that generous. I do have a Z51 C6 OEM rad/fan setup, but the rework to get a fit seemed extensive.

I'm using the E38 ECU fan control functionality to control the fan ... I'll need to play with the ECU fan settings with HPtuners to get it right. I'm not sure I understand your concern with turning the fan on ... re load on the electrical system. I can understand the current draw issue, but if everything is sized to handle the inrush on fan-start, what other concerns would/should I have?

Thanks!
eboch

 

Another question ... the E38 ECU starter relay control (pin 52) .... is that driven to +12V by the ECU when it drives the engine-start function? ... or does the ECU ground it? I ask because when I test it with a meter, it doesnt seem to be doing either. I dont have the APPS connected (missing a connector), so the ECU is throwing a bunch of APPS codes ... .would the absence of APPS cause the ECU to not want to try and start the engine?

Cheers
eboch

 

I don't know I thought all that starter relay stuff was part of the VATS system, and it was inter-connected with the BCM which you said you weren't using. What is the APPS connector for?

 

Hi 79LS1FOX;

You may be right about the starter relay output from the E38ECU (pin 52) ... it may be tied into the VATS. I noticed on LT1Swap.com that Brendo recommends deleting this pin/wire.

You're correct, I'm not running a BCM or TCM ....and have deactivated VATS in the E38 ECU.

I'm going to rewire the starter circuit so that its simply activated by the key-start-+12v line from the car's ignition switch. The assumption is that when the key is moved to the key-run position, the E38 ECU will get 12v on pins 19 and 47 and should therefore be ready to fire/run the engine as soon as the key-start position ignites the starter motor to turn the engine over.

APPS = accelerator pedal position sensor .... throttle-by-wire foot pedal connector (I'm using a C6 throttle by wire setup).

Cheers
eboch

 

Big fans can easily draw twice the rated current draw at start up, but you're right, if everything is sized properly, you will not have any issues. I just much prefer variable speed fan control. It's a much better solution than simply cycling the fan ON/OFF. Another fan option would be the C7 fan. You already have the functionality in your ECU, why not use it? Here is a good write up:

https://www.tbssowners.com/threads/c...ontrol.241568/

Andrew

 

GatTag0;

I do like the idea (good info ... I'll take a read). But I have this direct-fit electric setup for my C2 .... made for an LS-conversion. I need to investigate if the fan has any option for variable speed functionality. I didnt think about this to much when I bought it ... was looking more for C2 fitment and having the water-pipes on the correct sides, etc.

Cheers
eboch

 

You can use the C6 (Ford Fusion...same controller) controller with whatever fan you have. More info here than most people care to read...LOL

https://lateral-g.net/forums/showthread.php?t=40215

Andrew

 

...very interesting ... thanks!

 

Ok thats what I'm running with my setup just never heard it called APPS but yes I have a C6 pedal connected to a ZL1/CTS-V TB cause I just switched to a LSA supercharger, as far as pin 52 goes Speartech eliminated it from my harness so you should be ok with out it.