Diversions

My Speedo has been dead for a month or so. No speed reading, no odometer and no trip computer. A post on ls1.com.au and thanks to motomk I had a wiring diagram and some disassembly instructions. Cool.
I knew the VSS sensor was working as efilive was logging road speed fine, so the problem was somewhere after the pcm. I also knew the speedo needle did work, because going into diagnostic mode the needle would wind up to 80 no problem. From the wiring diagrams I could see that the road speed signal also went to the cruise control system just prior to hitting the instrument display. Ok, so I tested the cruise control and guess what. It worked. I now knew the issue was between there and the speedo.
It was then that I recalled someone posting up an issue with UK spec HSV's basically an aftermarket device was fitted to convert the signal to miles from kilometers and it had problems.
A quick search on pistonheads.com and good old Steve had posted up some info from his VTSS. He had removed the device and resoldered it.
Now I knew what I must do.
Armed with this information I set about pulling the dash apart. First problem, no stereo removal keys. No problem, just bend the stereo bracket to clear the console!

All disassembled and instruments removed. Now where is that evil device!
Aha, here it is.

Now going into here is a red and black wire. Steve assumed power and ground. Id agree as it comes from a different section of wiring, likely needed to power satans spawn. Out of the device came an orange and green wires. Now thanks to motomk, I knew the wire from the PCM for the speedo was Violet/White, I could see that Violet/Red was cut and rejoined with a short piece of blue wire, no junction just cut. I can only assume the pleb who's job it was to fit these things cut the wrong wire first and had to fix it. So anyway I could see Violet/White was spliced to green which went into the device and orange was spliced into Violet/White up to the instrument connector. Up to this point my intention was to solder up the device to fix any dodgy dry joints and reassemble. However why not just remove it alltogether!? I knew I could use PCM table H0105 to correct the speed signal coming from the PCM, so Id save messing about, increase reliability and gain about a billionth of a second over the 1/4 mile due to the weight reduction, so I thought Id leave it out.

Here is what Satan's spawn looks like up close and personal. The capacitor next to the incoming wires was broken loose and just wobbled around. If you wanted to fix it, then this would be the repair you needed to do.

So I just reconnected the Violet/White wire together and taped the whole lot back up. Job done.

Take it for a test drive. Now reading Km, but not for long. By the way, I dont recommend test driving with just the instruments and not plugging in the power windows, indicators etc when its 28*C outside, it gets kind of hot.
The only thing Im not sure of is how the Odometer will read if I just rely on changing the PCM output signal. Im hoping that given its only one wire that was being messed with and it seemed to handle the odometer as well as trip computer and speed needle, then I will be fine. Worse case Ill have to pull out the dash again and wire Satan's spawn back in place. Ill update in a few days to report what the deal is.

On a more PCM based note. Im now running EFILive custom OS5. It works fine and takes OS3 calibrations. Basically it extends OS3 by adding switchable timing and fueling for NOS applications. You could also use it to pull timing based on a switch for fuel octane variances.

It also supports Alpha-n fueling which is purely determined by Throttle and RPM, no other inputs such as MAF or MAP etc are used. Its really designed for hellish cams that wont hold or give a vacuum or stable airflow reading. (I wish that was me!)

So Ill be likely making some comments on that in the future given thats now my PCM OS d'jour. So its goodbye to OS3 and hello to OS5.