t2d2

iTrader: (8)

While pulling my ECU out tonight to take it to the guy who's going to replace my capacitors in the morning, I noticed four of the wires have been spliced. Here's a schematic of the wiring I remembered seeing in the A/T solenoid bypass thread:

https://www.clublexus.com/forums/4448576-post112.html

According to that numbering, the four are: 49, 50, 68, 69. All on the left side of the middle plug. 69 connects to a thick red wire and the other three all connect to thick brown wires. 49 and 50 look like speaker wire coming out of the plug. The other two were white/red and red/white wires, I believe.

I'm searching around for what those terminals represent to figure out what might have been spliced and why... If anyone has any suggestions what to look at, that would be appreciated. It might be something as simple as someone was too forceful tugging on the connector (you have to unscrew the bolt to back the big double-plug out) and had to hook up new pins after tearing them out (but why then cut the wire and splice a new length in, unless they couldn't get the old pin off the wire without shortening it?), but I'd like to at least figure out what they're for to know if they're related to any issues I've been trying to solve.

soarer13oy

iTrader: (13)

Its all normal i dont think you have anything to worry about.

t2d2

iTrader: (8)

Okay, I found it on FI-126 of the FSM. I think I got the pins figured out, having been off one with my count due to the unused (plugged) one on the bottom row.

#49 = RH (No.2) Knock Sensor
#50 = LH (No.1) Knock Sensor
#67 = OXR2
#68 = LH Sub–Oxygen Sensor (OXL2)

I'm hoping that's coincidental, seeing as I've had problems with Code 55 (knock sensor) from time to time. Actually, maybe I'm hoping it's not coincidental... A bad connection right there at the ECU would be a hell of a lot easier to diagnose than an actual knock sensor or sub-harness bad wiring issue! Does it seem plausible that that could be the source of the problem?

t2d2

iTrader: (8)

Normal as in, that sort of thing is seen frequently on these old cars, or that it looks properly patched back up?

soarer13oy

iTrader: (13)

Normal as in it comes factory that way. Those wires are shielded wires.

t2d2

iTrader: (8)

Really? That looks pretty ghetto for factory wiring, especially the two speaker wires. Why would they only be like that for a few inches? I guess I need to go look for pictures of more ECUs...

soarer13oy

iTrader: (13)

Its like that because its a shielded wire. Its like running two wires into one. The outer wire is like a noise filter wire it gets grounded. That ground wire does not go into the ecu which is why they remove a few inches. Just google a shielded wire then youll see how it looks in the inside.

t2d2

iTrader: (8)

Okay, that makes sense in terms of grounding and shielding. I'm still surprised/skeptical the factory would use speaker wire, though. That sure looks like it was repaired by someone.

This is the best picture I've been able to find of a 1UZ ECU's wiring:

http://carpron.com/multisite/d/41778-2/100_0330.JPG

It doesn't show much, but it sort of looks like there are some similarly spliced/wrapped wires down at the bottom.

t2d2

iTrader: (8)

A few morning (daylight) observations to add:

1) The right-most of the two speaker wires into the shielding sheaths is for knock sensor #2, which is the one I've had problems with. The red tape on its splice is loose, as can be seen in the pic, and sliding it down (didn't have to unwrap it), some of the wire strands can be seen sticking out of the sheath at the splice. How would I go about testing that wire to make sure both the signal and ground are performing as they should?

2) Terminals #71/72 are at the bottom right of the left-most plug (not pictured above) and are for the main O2 sensors. I figured it's worth unwrapping the electrical tape around the wires going to that plug to see if they also are spliced into grounding sheaths like the sub-O2 sensors (#67/68). They're not. Any idea why they would be different?

soarer13oy

iTrader: (13)

If it bothers you that much unpin the wires and use heat shrink. If you think thats ghetto wait until you open up the harness. There is worse looking electrical taps.

t2d2

iTrader: (8)

Well, it bothers me because it happens to be the wire for something that has been problematic. If there's a chance of a bad connection there, it's certainly worth investigating. Is the wire from the plug just stuffed into the sheath of the big brown wire, or are they soldered? With those bare strands of speaker wire sticking out, it seems like it's not as sound of a connection as it would have been originally.

t2d2

iTrader: (8)

Aha, I just remembered, I have seen another ECU wiring pic elsewhere, and indeed it shows the same speaker wire and shielded splices as mine.

https://www.clublexus.com/forums/per...lator-vsv.html

Same red and black electrical tape, even. That supports the notion that it's all original and makes it less likely that I have a wiring problem there.

t2d2

iTrader: (8)

Bad news may have just turned into good news... The tech that was working on replacing the capacitors on my ECU called this morning to say that he found bad corrosion under one of the caps and doesn't think it's worth continuing with the others. I went over to take a look before he puts the old one back in, as it's a 10th one I wasn't aware of that's tucked under the thick metal bracing that surrounds the wiring plugs.

Sure enough, the traces are nearly gone at C106, and looking it over closely, we realized the pins that connect to the board there are also pretty corroded. Having just posed the question in this thread about ECU wiring and pinouts, I instantly recognized the damaged section as being at the base of pins #49/50 and #67/68. I'm hopeful that that explains the sporadic knock sensor trips, being a very weak connection from the wiring to the board, and prone to losing the connection as things expand and contract from heat.

He said the capacitors all look original and the two he took off and checked are reading properly, with no signs of leakage. The damage looks to be from water having gotten in there at some point.