VSV6 ECU weird goings on.

[brett_jjj]

Hi,Im trying to work out whats happening with my VS,Its november 1995 VSV6 auto.The memcal I have is BSTK,apparently this was supposed to be replaced with BTXP for cold hesitation and pinging.( neither of which Ive ever experienced using this chip.)Anyway,If I try to change to a newer bin file like BTXP,BWPJ,or CKUL,I get error code 78 showing up ,I also get erratic oxygen sensor readings and behaviour,and the LTFT-STFT show erratic readings too.As soon as I go back to the BSTK bin,it all works fine again.Ive tried this on different memcal units and with a different ECU,and got the exact same result.Now I was thinking,(look out everyone),that if holden replaced the BSTK bin for the BTXP or later bins,its gonna cause this 02 sensor problem like it has for me,I wonder if this ties in with the 02 sensor earthing problem some VS's have.I get the exact same symptoms as a VS with the 02 sensor earth problem,but when I go back to BSTK bin,its all fixed and works perfectly again.Id like to hear any thoughts on this.Thankyou,Brett.

[Holden202T]

this is a strange one .... firstly because when i lookup 78 DTC i have a few sources, one says lh and rh long term fuel trims differ .... (this may be due to O2 earth issue) then my other source says blm cell calc error ... which is different but similar thing that its refering to...

SOOOO my suggestion .... use ckul or whatever you want .... before you put it in, remove power the the pcm for 20 mins or so to make sure you reset all the learning stuff, then see how it goes ....

if you still get the 78 DTC then maybe worth trying the earth fix mods.

really though without a log to see what your o2 sensors are doing your sorta throwing punches in the dark.

[delcowizzid]

could be as little as 1 setting making it go over the preset limit which is showing the code where the old tune didnt but the earth error was allways there just the tune stopped it from hitting its trigger limit for the cel ide do the earth mod

[brett_jjj]

Thanks guys,its weird.I thought it was the changes Id made to the timing etc,but Ive found that the standard bins also do it.(except BSTK).The only bin that runs with no errors is the BSTK one.Ive tried leaving the power off the ECU for a while to let it clear itself.Ive also tried a completely different ECU that I have as a spare,but the exact same thing keeps happening.This other ECU also had the BSTK chip fitted when I got it..I know another guy who uses the CKUL bin in his VS (his is the 2 wire 02 sensor version)and he has no problems with it.I just might do the 02 sensor earth mod,and go from there.I will get back to you to let you know how it goes,Thanks again guys for your time.Cheers.

[Holden202T]

one suggestion for the earth mod....

the info i found on the net shows you jumper wires between all the earths ..... what i did was strip the tape back a bit on the loom and then find all the earths and cut away the sheath on all of them for about 1 inch, then get your earth wire to run to earth on the car, strip it back about 2 inches on the end, then wrap it around all the striped earth wires to link them all together, then solder the whole lot.

tape it back up and you'll never know it was done other than an extra earth wire coming out of the loom!

[The1]

depends how keen you are, i did a few cars i ran cable right back to the earth terminal on the battery from the earth on the loom near the plug sockets, most of the factory setups have that half plastic protection stuff so you can put it in with the rest of the cabling.

[Holden202T]

i wasn't that keen

[brett_jjj]

I found a how-to for the 02 sensor fix on JC.I was reading through it,now it says that this 02 earthing problem occurs because the 02 sensor signal,and 02 sensor heaters,both share one common earth,this causes them to interfere with eachother and this interference stuffs up the 02 sensor signal..Is this right? If so,how would adding another earth to the body from the ECU earths fix the problem,the 02 sensor heater and signal lines are still going to be sharing the same common earth wire,which would still cause the interference, wouldnt it? Just doesnt sound right to me.Wouldnt it make more sense to clean the earthing point where the ECU earths at normally,and also run completely seperate earth wires for the 02 sensor heaters? Also, does anyone know where the ECU wiring actually earths (connects) to the body or engine?

[brett_jjj]

G'day again peoples,Id really appreciate hearing some thoughts about this before I go ahead with the earth mods.I still think that running seperate earth wires for the 02 sensor heaters would be the go.I just dont see how an extra earth at the ECU will stop the interference.(Thats if the shared earth is what actually causes the problem in the first place)Even with the earth mod done,the 02 sensor heater circuit, and signal circuit will still be sharing the same earth.I dont see how this extra earth will stop the interference between the two.(unless the ECU or the ECU wiring has a bad earth connection in the first place.) Thanks again guys.I appreciate any info or opinions.

[VL400]

I dont even think holden know what the deal is as the factory diagram is wrong!

VSOxySensorWiring.jpg

It could be that the engine earths are in different locations and your getting a ground loop.