Knock sensor circuit operation?
02-25-2014, 11:34 PM
#1
Melting Slicks
Thread Starter
Knock sensor circuit operation?
Hello, I have a 1985 Corvette and I want to be notified when the computer detects a knock. Since my computer doesn't data log knock counts, I would like to do this with a light bulb hooked up to the knock sensor circuit in a parallel circuit.
Since the knock sensor emits a low voltage reading I assume, I believe it goes to the ESC module and then signaled out to the ECM, I would like to tap off the wire from the ESC to the ECM, if that's how it works. At this point I'm only making assumptions as I haven't seen a wiring diagram for it.
Can anyone provide a diagram or an explanation including wire colors and possibly terminal numbers for the knock sensor circuit?
Thanks a lot!
Since the knock sensor emits a low voltage reading I assume, I believe it goes to the ESC module and then signaled out to the ECM, I would like to tap off the wire from the ESC to the ECM, if that's how it works. At this point I'm only making assumptions as I haven't seen a wiring diagram for it.
Can anyone provide a diagram or an explanation including wire colors and possibly terminal numbers for the knock sensor circuit?
Thanks a lot!
02-26-2014, 12:04 AM
#2
Race Director
I've seen a stand alone knock sensor device that uses it's own knock sensor and lights up a row of led lights. The more knock, the more lights light up.
02-26-2014, 02:14 AM
#3
Race Director
Here ya go:
My '86 FSM shows the knock sensor to ESC module wire as dark blue, so I don't know what's up there. For your application you don't care.
The pulses out of the ESC module are very short, so a light bulb wouldn't work. You need an LED with a relatively low value resistor. I would go with around 100 ohms. That should give you a flash that's bright enough to see.
Note that the ECM tests the ESC circuit by advancing the timing when you first start the engine, so you will get a couple of knocks at startup. The ECM will set an error code 43 if those knocks are NOT there.
My '86 FSM shows the knock sensor to ESC module wire as dark blue, so I don't know what's up there. For your application you don't care.
The pulses out of the ESC module are very short, so a light bulb wouldn't work. You need an LED with a relatively low value resistor. I would go with around 100 ohms. That should give you a flash that's bright enough to see.
Note that the ECM tests the ESC circuit by advancing the timing when you first start the engine, so you will get a couple of knocks at startup. The ECM will set an error code 43 if those knocks are NOT there.
02-26-2014, 10:09 AM
#4
Melting Slicks
Thread Starter
Here ya go:
My '86 FSM shows the knock sensor to ESC module wire as dark blue, so I don't know what's up there. For your application you don't care.
The pulses out of the ESC module are very short, so a light bulb wouldn't work. You need an LED with a relatively low value resistor. I would go with around 100 ohms. That should give you a flash that's bright enough to see.
Note that the ECM tests the ESC circuit by advancing the timing when you first start the engine, so you will get a couple of knocks at startup. The ECM will set an error code 43 if those knocks are NOT there.
My '86 FSM shows the knock sensor to ESC module wire as dark blue, so I don't know what's up there. For your application you don't care.
The pulses out of the ESC module are very short, so a light bulb wouldn't work. You need an LED with a relatively low value resistor. I would go with around 100 ohms. That should give you a flash that's bright enough to see.
Note that the ECM tests the ESC circuit by advancing the timing when you first start the engine, so you will get a couple of knocks at startup. The ECM will set an error code 43 if those knocks are NOT there.
02-26-2014, 11:08 AM
#5
Drifting
You're sure spending a lot of time with the 6870 that would be better spent with the 7165? Also, be careful when using the knock sensor to tune for spark. Larger cams and valve geometry can create harmonics that may be picked up by the sensor that are not detonation.
02-26-2014, 11:47 AM
#6
Melting Slicks
Thread Starter
I can't afford to go to the 165 at this time.
02-26-2014, 07:50 PM
#7
Drifting
02-26-2014, 11:00 PM
#8
Melting Slicks
I provided him a list of parts and the costs. When he decides to pull the trigger I'll be happy to provide the procedure I documented when I did mine. It took me the better part of a day to make the swap. The tuning has a much longer learning curve.
06-05-2015, 04:11 PM
#9
5th Gear
My 85 also has code 43 issues!
I have replaced the knock sensor, the ESC, and the ECM.
The timing is set at only 4 degrees advanced and I run only premium fuel. The system is working because as soon as the check engine light comes on I can feel the timing retard. Please help
The timing is set at only 4 degrees advanced and I run only premium fuel. The system is working because as soon as the check engine light comes on I can feel the timing retard. Please help
06-05-2015, 11:29 PM
#10
Race Director
You should start your own thread. Otherwise it gets confusing when the answers to YOUR problem get mixed in with the answers to the original poster's problem.
06-08-2015, 04:27 PM
#11
5th Gear
