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Old 09-07-2020, 06:59 PM   #1
Mr. V
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Location: Portland, Oregon metro
Default 940 knock sensor issue

1992 940 Turbo.

Car keeps throwing this code: 1-4-3; I clear it, fire it up, it returns.

Book says "knock sensor."

Bought a new one: no change.

Checking the wiring diagram, it shows each wire has a straight shot to the Jetronic ECU without it connecting to any other wires.

I unlugged the ECU from its wiring big connector, and then unplugged the small, two wire connector from the knock sensor.

Then I tested each of the wiring ends on the knock sensor connector with a VOM, touching the red VOM lead on the plug's wiring connector and having the black lead of the VOM hooked to ground.

I should have an open circuit for each wire, with no continuity: the green wire is open but the black one shows continuity.


I am guessing that somewhere inside the wiring loom the black wire is touching / shorting against another wire, but have no clue where it might be or how to troubleshoot and locate it.

I cannot back test it from the big plug at the ECU as there are no pin numbers visible and I have no ECU pin diagram to refer to.

What to do?
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Old 09-08-2020, 06:46 PM   #2
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Join Date: Nov 2002
Location: California

I found an EZK diagram quickly using google.

I see pin 12 and pin 13 at the EZK go to knock sensor. Test for continuity between each knock sensor terminal and the corresponding terminal at the the EZK box. If you look closely you can see numbers. Or just go from one corner and guess that it's terminal 1 and then count to terminals 12 and 13 AND go by wire color. It's tough to see the number 1 marking, especially while you are contorted in a dark footwell, but it is there.

BACKPROBE ONLY. Do NOT stuff meter leads into the front of terminals. Only frontprobe with the correct test probe. You can make some test probes using male terminals from old components.
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Old 09-08-2020, 09:53 PM   #3
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This is the proper way to test the ECU connector. I believe the EZK connector is the same.

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Old 09-08-2020, 10:26 PM   #4
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Originally Posted by Mr. V View Post
I unplugged the ECU from its wiring big connector, and then unplugged the small, two wire connector from the knock sensor.
The knock sensor goes to the EZK box, not the ECU. Try unplugging the EZK (above the driver's feet, next to the steering column). There's some trick needed to get the bracket unscrewed properly - I've never figured it out on the junkyard cars that I've pulled the EZK from. If the EZK connector is not unplugged, one of the knock sensor wires connects to ground through the EZK circuit board, which is why it has continuity to ground.
'85 245glt b21ft aw71 k-jet -> lh2.4
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Old 09-13-2020, 01:30 PM   #5
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Location: Seattle, WA

It might be an electrical problem. But to be thorough you could take the knock sensor off the block and leave the wires connected. Maybe it does actually detect something in the engine. Just a thought.

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Old 09-13-2020, 01:33 PM   #6
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Don't forget to torque it down properly as the sensitivity is increased the tighter it is.
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