oldgoat69

I am installing a set of Speedhut Can-Bus gauges into my 2003 LQ4 equipped vehicle. The instructions say that I should have 5 pins in the OBD port to support CAN J1979 protocol.
PIN 4 - chassis ground
PIN 5 - Signal ground
PIN 6 - CAN high data
PIN 14 - CAN low data
PIN 16 - 12 volt

My OBD port is wired:
PIN 2 - Serial Data
PIN 4 - Ground
PIN 5 - Ground
PIN 16 - 12 volt

I have used a Bully Dog monitor up to this point with great success. It is compatible with all GM PCM's from 1999 to date. When did the wiring to the OBD port change, and is it possible to retro fit to my PCM?

gofastwclass

iTrader: (2)

I wasn't aware that the 2003 controller was CAN bus. If it isn't (and I don't believe the P59 controller is) you can't run those gauges because they can't communicate with the PCM which only runs OBD II (J1850) through the Serial Data wire (pin 2).

The change for most GM vehicles was around late 2006 or 2007 with the mandate for the 2008 models. No, it's not as simple as adding a couple of wires so it isn't possible to retrofit your PCM.

oldgoat69

This is not really bad news, since one of my next upgrades was going to be a 6L80 trans anyway. Which PCM should I be looking for? Is it possible to use the existing harness and just use the newer style PCM connectors?

gofastwclass

iTrader: (2)

I hate to be the bearer of bad news and someone feel free to correct me if I'm explaining this poorly or improperly.

If I'm correct anything that can run a 6L80E will be CAN bus and every CAN bus PCM I've seen had different physical pins than you have to match the different connectors. I'm not even sure the pins are the same across the various potential PCM's you could use.

I also believe the 6L80E's work with a separate transmission controller on the CAN bus network which may or may not be located inside the transmission depending on year and transmission model (not sure about 6L80E's). The PCM's are also all 58x instead of 24x which means swapping the reluctor wheel on the crank and cam or buying a conversion box. I know someone makes a conversion box, but I can't remember which way it goes. Then you would need to have the new PCM uploaded with a calibration that is compatible with your engine combination, then adjust shift points according to your gear, tire and driving style.

If you want the 6L80E someone probably builds a stand alone harness and controller for it but I don't have any experience with that.

This sounds like a complicated and expensive proposition just for a set of gauges.

I'm sure there is more, but I'm at lunch trying to get rid of a headache and these are the first things that came to mind.

slow

iTrader: (7)

you need to change the reluctor on the cam and crank to run a E38/E67/E78 to work with a 6Lxx trans. no you cannot use the same harness.

LPE makes a 58x engine to 24x computer box, but not the other way to my knowledge.

only the E40 Ecm will work with your current engine and have can bus, but it will not work with the 6Lxx trans.

Ryan

oldgoat69

It does not really matter that the 6L80 won't work out. I may eventually end up putting the entire works into my S-10 and going a later LS3, that was the original plan anyway. As long as I can make an E40 and the proper PCM connectors work, I am golden.