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Coolant Temp Sensor Issues and ECU Troubleshooting

Few more questions that I could use some help with.

First I have some more pictures of the wiring harness to the fuel ECU. Curious about whether this ground wire coming out of pin 5 is right. Should it be spliced and connected to the green wire coming out of pin 24 like it is currently or is that an issue? Reviewing the wiring diagram there appears to be two wires that share pin 5. This appears to be correct but I just want to make sure as you all can easily gather I'm still learning the electrical side of things.
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Also the wire on pin 13 has lots of play and as you can see the connectors appear to be bent back, most likely from improper probing. When i started the car i did a wiggle test on that wire. Wiggling it caused the vehicle to promptly cut out. I feel this may be my problem. Thoughts?

If so, does anyone have leads on what type and where i can purchase these ECU connectors?

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The fat green wire going to pin 24 is a shielded wire -- there's an inner wire, a layer of insulation, a tube of wire (the shield) and then the outer insulation. The inner wire goes to pin 24 (O2 sensor) and the shield gets pulled off to the side and goes to pin 5 (ground). That's the way it comes from the factory.

Pin 13 is the coolant temperature sensor, and yes, a loose contact there could cause problems. You can find replacement pins at Dave Barton's 240turbo.com site, or scrounge a section of harness from a junkyard and splice in a good wire with good pin.
 
That terminal is damaged. Probably from an amateur front probing it with a meter probes. Replace it. It can be tricky to get them out without damaging the connector.

We do "drag tests" commonly to find loose connections that can't even be seen. I drag the proper tool in and out of the terminal to feel if its lost tension, making a poor connection. I make them out of pins from old components. I solder a wire onto them for making electrical measurements. I made a bunch and handed them out to some of the guys and they actually use em!
 
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Hopefully this will be my last question and will bring an end to this issue. I apologize for my lack of understanding and probable thick-skulled-ness on this thread.

So I found that the connector to the ECT was loose and damaged. I cut off an EV1 connector from a bit of injector wiring I had laying around. I rewired this to the existing ECT wires and it is a much more secure fit.

I also discovered that the connector to Pin 13 was loose and damaged from improper probing from the front and so a new connector was purchased from Dave Barton's site and was crimped and rewired and has shown to work and fit much better.

I took my multi-meter and a newly obtained section of wire (as i should have done from recommendations from bobxyz and ZVOLV) and began testing wires. Setting the multi-meter to test for continuity. I checked both wires from the ECT connector to their rightful plugs on the LH and EZK ECU's. Both checked out.

On to the grounds. I checked grounds on both ECU's. I disconnected the forward ground wire on the intake and wrapped my test wire around the ring terminal. This is the ground that has been talked about much with the 4-1 splice. Pins 5,19, and 29 on the LH and pin 20 on the EZK ECU's all received a beep from the multi-meter showing continuity from the ring terminal to all four pin connectors. Pin 17 was tested and checked out with the multi-meter grounded at the cigarette lighter. I also pulled the protective shroud off of it and inspected the condition. It is pictured here. I do see a bit of exposed wire right after the main splice but I do not know if this would be a factor. Maybe this could cause problems with engine vibration.
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The reason I am posting is because I am again receiving the 1-2-3 code on Pin 2 of the OBD. More interestingly, and what has lead me to believe that this is ground related, is that pin 6 for the EZK is now showing a 2-2-4 code. I have not seen the car show this code since I first posted but it has again returned accompanied by poor cold start performance, random engine shutoff, rich mixture, and very poor "lopey" idle upon initial start.

From what I am gathering here it appears all my wires are fine. This makes me question either the Engine ground strap to the fire wall or my ground connection on the intake.
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Again thank you all for the help and apologies if I'm like talking to a brick wall.
 
That ground wire is clearly shot. Good find.

Between repairing that ground wire and repairing the signal circuit you should be good. Maybe somebody was in there before and bent the terminals, but overlooked that bunk ground wire and gave up. The ground side of circuits is commonly overlooked.
 
Sorry I haven't read this whole thread.

I had a similar problem to this in my 90 240. There is a joint in the wiring harness that had broken.
 
That ground wire is clearly shot. Good find.
Fixed it and the vehicle hasn't had issues since! Fingers crossed this was the fix. Just waiting for the ECU to relearn.

I had a similar problem to this in my 90 240. There is a joint in the wiring harness that had broken.
Can you post a pic of what you are referencing? Would be good to at least check this or have something online for people to reference in the future.
 
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