A quick search seems to show that nothing has changed since the old code 52 days, and PO325 is strictly an electrical issue - P0325 OBD-II Trouble Code: Knock Sensor Malfunction (Sensor 1, Bank 1)

Unless you can find a reliable source otherwise I wouldn't spend any time on fuel trims or anything else outside the circuit.

I've got another one showing 22 and 23 on E9, but oh well, as long as you're getting continuity they're most likely the right ones (there's your ground point, BTW). Did you check for continuity between each wire-run terminal end at ECU, while disconnected, and a known ground? If it's there, you have a short. Easy fix, just splice in some new wire near sensors, preferably shielded but not critical and then splice to ECU ends. Just noticed the note about crushing it if fault was in ECU harness. Is that main engine harness run what you're referring to as ECU harness?

Scotchlock trick seems like it'd work in some cases, like if you have one bad sensor, although if you do it over a shielded portion you'd short the signal to ground, and if there's a ground short elsewhere in the wiring, further downstream etc, it seems like you'd just short out both signals.

I'd start with depinning both wires from ECU plug, clamp them together and test for continuity between them at other plug end (one prong on each spade), and then test for continuity between each wire and ground. Continuity on first test =pass , on second test= fail.

When you say you tested continuity with everything installed, you back probed the end of the KS pigtail, on the KS side, and tested that to the ECU terminal? Good for you if so, but not commonly done, and I've seen loose and corroded female spades cause issues several times before. Not likely to be your issue if it's all new though.
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Good find on the vacuum line, that couldn't help at all!

The ECU ground is inside near the passenger's side kick panel I believe. Been a while since I've looked for it. If it's not easy to get to, don't worry about it too much unless that's your last resort.

You'll find that problem wire, it's in there somewhere.

So an update: Code cleared itself so I went for a drive. Couldn't seem to trigger it until, again, turning her off and back on again. So i decided to hook up the scanner to it and got a surprise. The code has now switched from P0325 to P0135 (O2 sensor heater), and while browsing with the OBD, one O2 sensor shows the voltage is roughly half of what it should be... Think that might be the problem

No, but sounds like you have a damaged wiring harness

Look for melted or pinched loom

Haven't found anything yet, the only set of wires that needed replaced was ironically the knock sensor harness, which was brittle like glass. Everything else wiggles around freely and looks fairly in-shape - I've actually redone some of the looms because I couldn't stand how they were done; namely the SUPER brittle ones alongside the fuel rails, and didn't notice anything besides some soot and dust

Today it took some doing to get the CEL to come back (thought I was in the clear), now I have P0325, P0330, and P0135...
Anybody have any ideas? There has to be a common denominator in here somewhere. Gonna replace the O2 sensors since they have thrown a code before - but that's about where the correlation stops

Did you check for short to ground on your knk conductors yet? Seems pretty likely that's what's going on, and that it's intermittent so might not even show up without repeated testing. If it was me at this point I'd just run new shielded conductors, splice to connectors and and cut off the old conductors. It's like $10 and maybe a couple hours work. You've already replaced everything else so even the testing is kinda moot at this point really, the purpose would be to rule out the expensive stuff like the ECU replacement (although if it's automatic that's not really so expensive generally

Swap out the engine harness. Even a junkyard unit would be an improvement.

Just wanted to ask a quick question, but I was wondering about the fuel trim - how long does it take to reset if the battery disconnect, and what is considered normal for the long term fuel trim.

I would recommend to get the short and long fuel trims as close to zero as possible by first starting by cleaning the MAF and air filter, checking for vacuum leaks, and if the 02 sensors are original (or A/F sensor if ya have one), replace them.

If you don’t have access to a smoke machine but have a code reader that reads live data, see how the fuel trims read after a drive cycle. If the long term value is at least 5% greater/less than the short term at idle, and if you rev up the engine to around 2000 rpms and the trim levels come close to zero as they should be, more than likely there is a vacuum leak somewhere under the hood.

The negative cable off the battery for at least 90 seconds resets the ECU.

So you are saying if the Trims are +/- 5 of eachother at warm idle, and when I rev to 2k rpm the trims go to zero there is a leak. Do you mean that the trims will add to zero?

Ie Long term trim = 5%, and at 2000rpm and short term fuel trim goes to -5%?

This it the fuel trim LTFT.STFT. The Long Term is the whole number and the Short Term is the right of the decimal point.

Everytime the short term hits +-30 it adds or subtracts a 1 to the Long Term value and then zeros out the short term value.

Long term between 10 and -10 is what most refer to as normal.

What is your MAF reading at idle? That does a good job of telling you if any combustion air is bypassing the throttle body.

My two 97’s run zero for the LTFT most of the time but the highest I’ve ever seen on either one was 3.


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I thought about this after the new ECU failed to fix it, but i dont have the first clue where these wires start and end up. How hard of a job is it?

For a general understanding, yes. Zero or close to it is ideal. The older autos get the more likely you will see a small vacuum leak due to age, but unless there is a tear or forgets to reattach a hose, it probably won’t trip the money light. Fuel pressure also plays a role here.

10% or less between trim levels and you should be fine at idle, thus you should be fine with your numbers at idle.

This is a good read and may help further explain it:
MAF Sensor Testing Methods - Tire Review Magazine