• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

1-4-3 Knock Sensor code

Uncleknucklez

bruspeed
Joined
Apr 15, 2006
Location
Sacramento, CA
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?
 
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.
 
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.
 
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.
 
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.
 
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. :roll:
 
That would have been a drag, and something like that would have taken me forever to figure what was wrong with it. :roll:

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.
 
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 :)

544ecu10.jpg
 
Back
Top