Knock Sensor; What happens if its disconnected

[LGAFF]

Could not get this answered on the other forum, if the knock sensor is disconnected does the ECM retard timing?

[Kevin]

no the ecm does not retard timing since it doesn't detect knock. disconnecting it does nothing positive for you and can only end up hurting, at least according to Haibeck

[LGAFF]

I did not disconnect, it was disconnected when I put it up to change the clutch. 101 projects for your corvette says it retards timing at WOT, when it is not hooked up.


If ECM does not detect resistance it retards a precaution...per the book. Checking to see if this is accurate.

[Kevin]

Originally Posted by LGAFF

I did not disconnect, it was disconnected when I put it up to change the clutch. 101 projects for your corvette says it retards timing at WOT, when it is not hooked up.


If ECM does not detect resistance it retards a precaution...per the book. Checking to see if this is accurate.

this would make sense...my first post may have been wrong

[XfireZ51]

Lee,

Looking at the FSM and reading the Diag Charts and reviewing of Code 43, the ECM only retards timing when it receives an AC signal produced by the KS. There's no indication that the ECM goes into a "default" timing if it doesn't "see" the knock sensor. If there's an open circuit, as in your case, then a voltage of either >3.62v or <1.44v will cause the ECM to set a code 43 after 24 seconds. I don't have an answer as to why you don't have a code set.
There's a second test the ECM will run under the conditions of Coolant at > 93C and High engine load. If the ECM does not see a response from the ECM, a Code 43 will be set. I also remember that the GN guys would pull the knock sensor connector to avoid KR (Knock Retard). Of course, the LT-5 ignition could be different but the GN ignition is close as it uses Waste Spark.

[LGAFF]

I guess we will find out when the clutch goes back on, I would think there would be some kind of protection for the engine in the event the wire came off.

[XfireZ51]

Originally Posted by LGAFF

I guess we will find out when the clutch goes back on, I would think there would be some kind of protection for the engine in the event the wire came off.

That's what the CEL is for.

[LGAFF]

This is what the buick site says on the GN

CODE 43
Trouble Code 43 indicates that there may be a malfunction in the Electronic Spark Control (ESC) circuit.
ESC is used to sense spark knock (pinging) and retard the timing to eliminate it. A knock sensor (located at the rear of the engine block) sends signals to an ESC module which then signals the ECM that knocking is being detected. The ECM will retard the timing by as much as 20 degrees in 1 degree increments. A loss of knock sensor signal or loss of ground at the ESC module will cause the signal at the ECM to remain high. The ECM will act as if no knock is present, and may possibly result in engine damage, if there is detonation.
Loss of the ESC signal to the ECM will cause the ECM to constantly retard the timing to its maximum. This results in sluggish performance and a Code 43.

The conditions for setting this code are:

• Engine is running
• ESC input signal has been low more than 2.23 seconds

Typical causes for this code include:
1) Open or shorted knock sensor
2) Loose knock sensor
3) Excessive mechanical noise within engine
4) Improper or incorrectly installed PROM or CALPACK in the ECM or defective ECM
5) Intermittent open in the EST line to the ignition module

Originally Posted by LGAFF

This is what the buick site says on the GN

CODE 43
Trouble Code 43 indicates that there may be a malfunction in the Electronic Spark Control (ESC) circuit.
ESC is used to sense spark knock (pinging) and retard the timing to eliminate it. A knock sensor (located at the rear of the engine block) sends signals to an ESC module which then signals the ECM that knocking is being detected. The ECM will retard the timing by as much as 20 degrees in 1 degree increments. A loss of knock sensor signal or loss of ground at the ESC module will cause the signal at the ECM to remain high. The ECM will act as if no knock is present, and may possibly result in engine damage, if there is detonation.
Loss of the ESC signal to the ECM will cause the ECM to constantly retard the timing to its maximum. This results in sluggish performance and a Code 43.

The conditions for setting this code are:

• Engine is running
• ESC input signal has been low more than 2.23 seconds

Typical causes for this code include:
1) Open or shorted knock sensor
2) Loose knock sensor
3) Excessive mechanical noise within engine
4) Improper or incorrectly installed PROM or CALPACK in the ECM or defective ECM
5) Intermittent open in the EST line to the ignition module

Do you always use the Buick site for trouble shooting on the LT5?

Completely different animal. The LT5's engine protection is the SES, which limits your secondary operation.

Buick it has to cut timing, as that is it's only protection.

[LGAFF]

Looked at the GN site as prior note refers that both use waste spark and might be similiar.

Would a DRM chip shut off the knock sensor?


I would doubt that I did not have secondaries....... my MPH seemed slow but not that slow.


Looks like I will need to see what happens when I get it all back together. I was just surprised to see the knock sensor disconnected when I went underneath the car and there was never a code.