System/ECU voltage variations

[immortality]

Hi All,

I seem to have a voltage issue at the PCM in the missus V6. Alternator/battery are at 14.0-14.2 volts however the i'm only seeing about 13.2 volts at the PCM when data logging with the laptop connected.

Will this effect the tuning much?

I haven't yet been able to track down the reason for the voltage drop. I've cleaned/tightened battery terminals, cleaned the wiring loom earth points on the engine and body but no change so far.

Thanks

[krusty]

How's the alternator reg? Does it hold steady under load?

[Holden202T]

if its 14.2 that's what commodore regs normally are supposed to hold.

maybe go back through the power circuits to the PCM and check at relays etc, might be a dodgy joint somewhere.

[immortality]

As far as I can tell the reg is holding steady.

[immortality]

Did some testing this morning.

Alternator is holding a steady 14.21 volts on the rear output post.

I'm loosing about 130mV from the alt post to battery post, loosing about the same from battery post the back end of the EFI fuse. I changed the fuse and relay just in case.

Ran the car, hooked up the laptop, battery showing 14.1 volts but software is showing reading that fluctuates a little from 13.2-13.4 volts.

Did some back probing on the PCM and I'm seeing about 13.7 volts although I'll need to double check exactly which pins are power and earth pins.

I'll try another PCM and see if that makes any difference.

One of the terminals on the main fusible link is showing corrosion on the crimp connection so that will need to be re-terminated at some stage although I'm seeing only about 10-15mV drop across the Fusible link so I don't think that it's contributing to this particular problem.

Cheers

[immortality]

OK,

Fitted the original PCM, voltage reading increased to 13.5-13.6 volts (back probe was 13.7 volts).

Took it for a quick spin and took a log whilst I was at it. It looks like I could also have a alt reg problem as the voltage had dropped during various parts of the drive and when I got home.

Possible also an O2 problem as the #2 O2 sensor seems to show lean most of the time (Both sensors were replace some time ago as one wasn't swinging at all) and air temp seems to be a bit high as the ambient temp at he moment is about 24-25 degrees with the air temp sensor showing no less that 33 degrees. Car is fitted with MACE Cold air intake which previously has shown temps at or just above ambient.

LTFT's are a long way out which is odd as they were reasonably good at the start of the year, something has definitely changed????

Log attached.

[Holden202T]

I have seen regulator issues where its only once they get some heat into them they play up!

[immortality]

It could be, I'm thinking the charge lead could also be a problem when it heats up as well so I've started making a new cable at work, I wanted to use a slightly bigger diameter cable but we had non in stock so standard size will have to do. I'll measure it up today so that I can fit the crimp lugs at work tonight and I'll fit it this weekend. Once that is done I'll check it again and if it's no better than I'll look at replacing the alternator and/or regulator.

Cheers

[Holden202T]

if you want to test larger diameter wire use the new one with the old one still in place!

[immortality]

I was having a think about that corroded crimp joint, Having another look it looks like it's been hot I think. Talking to the sparky at work he's of the opinion that the standard size cable isn't anywhere near large enough to carry the maximum alternator output current for any length of time. Seeing the number of ecotecs that pop up on the JC forum with problems with the charge cable it does seem that Holden spec'd the cable to carry the nominal load but not peak load. Naughty naughty.....