Topic: Oh no, mot this! Knock sensor replacement.

[sirdeuce]

I hate it when this happens. Replaced the knock sensor on my 1990 2WD 3VZ. Well that was not the issue. Still getting the 52 code. So, removed the upper manifold to access the wiring. Pulled out the 'ol Fluke 77 and went-a-testin'. With the ECU and knock sensor connectors unplugged I get 2k Ohm between the 2 female connections in the KS plug, hmmmm. I also get the 2k Ohm from the connector to ground, NOOOO! So I put it back together so I can at least move the thing around. Now I get the 52 TC, along with 51 and 22. NOW WHAT?! No A/C in this truck, so the 51 is probably just the neutral switch, put the gear selector through it's range, that code goes bye bye. Phew. Now, for the 22, engine coolant temp. I can access that without pulling the manifold! Had a spare sensor, plugged it in to see if maybe the sensor is out, still got the code. Damn, 3.4 Ohm across that connector with the ECU disconnected. I have a problem in the harness.


This is a first for me on any of my vehicles. Most of the time I have to repair a harness it's because the owner tapped into something and jacked something else up. That's not the case here, untouched harness. Are there any kmown issues with this harness? I can't seem to find anything related, so I'm asking the good people here, any experience? Maybe someone has a clue that can prevent me from having to open this entire harness.

And, no, vermin haven't taken up residence in this truck, at least ot yet

[gnob]

Could just be crud in the conn. Could be pinched from your work.

[Snowtoy]

Did you replace the short section KS wire, along with the KS? 


The wire becomes brittle from heat exposure.

[sirdeuce [OP]]

No crud in the connector, wires mot pinched, tucked neatly next to the fuel rail.

Yep, changed the pig tail with the sensor.

[gnob]

Sounds like you have it under control then. :rolleyes:

[sirdeuce [OP]]

Don't roll your eyes, they'll get stuck looking at your brain. I took your thought into consideration gnob, got me to thinking, I'm not the only one to work on this vehicle. SO, I went out to check the harness, mani off, wires tucked nicely under the fuel rail, as I said. So I uncovered the wires to check for signs of crushing, none. But I did find the cold start fuel line has been crushed, not leaking, but crushed. Could be why this thing has a hard time starting cold. Gonna replace that hose before I reassemble it. Since I have the harness apart I can say there are no pinched, bare or broken wires, at least after the plastic guide behind the cam sprockets. Now I don't have the resistance between the pug terminals though. No foreign material in the plug. Time to dig deeper in the harness. I was hoping to avoid that. Worse scenario would be a melted insulation issue in the harness. Hopfully I don't have to dig too far.

[Snowtoy]

Have you checked the terminals at harness and the ecu?

[sirdeuce [OP]]

Yes, checked connections at both ends. I have continuity between ECU plugs and sensor plugs. I separated and insulated the circuits in the harness, even though I found no damage to the insulation. Seems to have done the trick, as far as testing with an Ohmmeter, I no longer have any continuity between plug terminals. See how things go after I put it all back together. Problem could be deeper in the harness than I dug, Might have disturbed whatever was causing the issue. At least if the problem reemerges later I know I don't need to take out the Manifold.