pcmhacking.net

Ok so as you know from the previous posts, I replaced the computer to fix the broken pins issue. ... at the time I took the gamble that the wring loom would be ok, but over time that turned out to not be the case, so I have recently replaced that, and so I decided to pull the pcm connector apart to see the damage, I wasn't expecting it to be this bad, but it certainly explains some of the issues I had!
in the process of all the stuff I've done with the car to fix the pcm and diagnose the faults caused by the wiring loom connector I have taken a heap of screen shots of GDS and SPS stuff and thought i'd share some of them for the greater knowledge of the fourm community.

So this is some of the fault codes I was seeing when the corrosion was at its peak
This is just some general browsing through GDS while I had spare time and to make the most of my subscription ... interesting the amount of info new cars keep tabs on!
I'm not sure how you actually make it over speed, unless it needs the rev limiter removed to do it ?
Just some immobiliser stuff for interests sakes while I was confirming both my keys worked.
If you ask it to do a crankshaft sensor re-learn it makes sure its up to temp then it lets you perform the test
Just some info when re-programming the new PCM with my cars correct calibration.
If you do a vehicle wide capture it spits out a massive amount of pages of info, pretty cool stuff for diagnosis or just generally to know what all the details of the car are.

WOW, that corrosion is really bad. Wouldn't have expected that in a modern car.

you and I both

I think the main issue is that once water got into the plug, it then connected a few ground and +12v pins together and made it into a nice little electrolysis experiment! I need to sit down and see which ones are the worst, but from diagnosis and pins that were not there, it was constant +12v power, there was a serial data bus line, and the fuel pump relay control (ground side) I think were the main ones.

cut the whole plug off and replace it I say, should be plenty to raid off in most pick a part wreckers.

not worth it, for $270 new loom ....

How'd the water get in there in 1st place ?

ok so some time ago, I had a coolant hose crack on the engine and this was spraying out in a nice jet mist onto the side of the pcm and the bonnet and general area.....

One would expect that the pcm plugs would be water tight, but my guess is as its in the engine bay and getting nice and hot, as it heats up it would expand and push out any air in there, but then as it cools down it draws air back into the plug seals, or in this case water!

the first time I could smell coolant when I got home I couldn't actually see anything and the coolant level wasn't low, so then the next few days I smelt it and eventually found the leak, but by that time the damage was done, the thing was, at the time I didn't know any water had actually got into the plug, so I fixed the coolant hose and went on my way, then the DTC's started coming up and eventually we get to the current issues

explanation of the layout of everything to make the above make more sense - these pics are just the best I could find on google!

this first picture is a different motor / thermostat housing, ignore that, its more the location of everything I'm trying to show here, and below the pcm connector you can see is another one, which is the one that has been corroded, i'd say the only reason water didn't get into both was because the top connector is behind the inlet pipe!
This is the same as my layout with the inlet pipe removed to show the offending pipe better.

I always questioned the motive for putting the PCM in the engine bay? The only logical answer I can see is to reduce the length of the wiring loom and save a cent per wire.......

yep that's right, but if you think about it in terms of hundreds of thousands of looms that few cents turns into a lot of dollars!

we'll say they save 1mtr of wire doing this, in the case of the cruze, that's 43 pins in J1 and 42 in J2, that's 85mtrs of wire, I just had a look at jaycar, hook up wire is 22c per mtr, that's $18.70 per car .... even if you say 50% because they get spools of wire cheaper, its still $9.35, multiple that by 100,000 cars that's $935,000 .....

I know if I had the choice i'd pay $20 more to get the PCM in the cabin, but as a car manufacturer they are only looking at cost per unit out the door..... it probably also makes things quicker on the production line too, other than whats on the motor theres only a few connections to body loom and fuse/relay panel and its in and done.... not that that's ever really changed much, but with cars being so electronic these days any way to save cabling has to help for weight, costs and simplicity.

I was starting to think you bought it from a Punchbowl rebirther after it went swimming in salt water. Good to see you found and fixed it bad to see how easy the damage occurred.