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Old 05-17-2017, 12:06 PM   #1
Uncleknucklez
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Default 1-4-3 Knock Sensor code

Hey all, 1991 940 b230ft, lh2.4 (in my 240), keeps throwing the 1-4-3 code "knock sensor signal absent or faulty"

That code does not mean knock detection correct, just means that the signal is bad from the sensor?

Just want to make sure, car has a slight stutter as it dips into boost, and then throws the code, is there anything specific I should look for?
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Old 05-17-2017, 12:19 PM   #2
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Your analysis is correct.

Try cleaning the connection before replacing the knock sensor.
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Old 05-17-2017, 12:26 PM   #3
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Are there any other codes? (Figured I'd ask) Yes, that would mean the system isn't getting a signal or is super crappy. Check the connections and grounds on the motor. Check and make sure the knock sensor is properly torqued down too. If you've kept up on maintenance, I am willing to bet the sensor is bad. Here's some more info https://www.volvoclub.org.uk/faq/Eng...ngaKnockSensor
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-My car: White 1991 244, 308k miles. B230F LH2.4, AW70, R134a retro. Thrush glasspack, anthracite refinished Coronas
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Old 05-17-2017, 04:09 PM   #4
ZVOLV
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I would inspect for pin damage at the connector.

I haven't refined my techniques here, but try tapping the block with a hammer and see if the ignition timing retards.

Or practice pulling the signal with a scope...

Or maybe practice looking at the fuel enrichment voltage.
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Old 05-17-2017, 04:13 PM   #5
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Originally Posted by ZVOLV View Post
try tapping the block with a hammer and see if the ignition timing retards.
This is another way to test for it. Most of us don't have lab scopes laying around, but if you find the scope fairy be sure and let her know I want two. But if you know someone that has a lab scope, get at it. I'm still betting the sensor is bad, from either corrosion or goo.
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Old 05-17-2017, 04:32 PM   #6
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Quote:
Originally Posted by oldschoolvolvo View Post
Your analysis is correct.

Try cleaning the connection before replacing the knock sensor.
I had that same code in my 92 740.I tried cleaning the connection and block as well and there was no change.Swap it out with a new one..perfect!
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Old 05-17-2017, 04:34 PM   #7
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If you've got to replace it, might as well replace the coolant temp sensor and intake mani gasket.
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Old 05-17-2017, 05:34 PM   #8
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Quote:
Originally Posted by KeizerBrickGuy View Post
This is another way to test for it. Most of us don't have lab scopes laying around, but if you find the scope fairy be sure and let her know I want two. But if you know someone that has a lab scope, get at it.
I will sell you my $80 Hantek for $60 shipped. It reverted back to Mandarin or Cantonese.

https://www.picoauto.com/library/aut.../knock-sensor/
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Old 05-17-2017, 05:36 PM   #9
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That's a heck of an offer ZVOLV...but as of current, I must keep my spending tight with a baby due in September.
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Old 05-17-2017, 11:36 PM   #10
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Problem solved. Pay attention to the wire colors folks, had the egr plug on the knock sensor, and vice versa. Why the same connectors so close together???

This thing runs pretty goooood now.

Thanks all.
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Old 05-18-2017, 12:06 AM   #11
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yes!
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Old 05-30-2017, 05:42 PM   #12
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At least it doesn't fry anything.

On the LH 2.2 cars the TPS switch and IAC valve connectors are the same and they're quite close together. If you swap those by accident it fries the transistor that controls the IAC valve and then the engine revs up to 2500 RPM as soon as you start it. Been there, done that.
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Old 05-30-2017, 05:43 PM   #13
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Originally Posted by James10952001 View Post
At least it doesn't fry anything.

On the LH 2.2 cars the TPS switch and IAC valve connectors are the same and they're quite close together. If you swap those by accident it fries the transistor that controls the IAC valve and then the engine revs up to 2500 RPM as soon as you start it. Been there, done that.
That would have been a drag, and something like that would have taken me forever to figure what was wrong with it.
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Old 05-30-2017, 05:51 PM   #14
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That would have been a drag, and something like that would have taken me forever to figure what was wrong with it.
I'm actually surprised I figured it out as quickly as I did, and even better I had a suitable NPN Darlington transistor in my junk box. Fried the ECU at 1am, had the car running properly again by 2am and my brother was able to drive it to work later that morning.

If anyone ever does the same thing let me know and I can point you to the part that is fried.
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Old 05-30-2017, 05:55 PM   #15
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Quote:
Originally Posted by James10952001 View Post
I'm actually surprised I figured it out as quickly as I did, and even better I had a suitable NPN Darlington transistor in my junk box. Fried the ECU at 1am, had the car running properly again by 2am and my brother was able to drive it to work later that morning.

If anyone ever does the same thing let me know and I can point you to the part that is fried.
It has occurred many times in my experience helping folks on the boards

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