Tech 2 - What does it do?

[studigggs]

So reading through the mt2500 GM diag manual, it says the 'ESC Counter' tracks magnitude and duration of knock sensor output from 0-255. Even on hard acceleration I'm not getting an ESC Count higher than 3, and above 40 mph when the 'knock' dummy light is constantly lit on the mt2500, the ESC counter is at 1.

What I'm trying to find out is what ESC Counter value (magnitude) is required to trigger timing adjustment? Can't seem to find a theory of operation on the ESC system that mentions this.

I have gone through the EGR and EGR Solenoid diagnostic trees and they are both fine. I even pulled the EGR to see if the passages were plugged and they were clear.

Fuel trims hover around 128, O2 cross counts are between 6 and 20, O2 mV bounces between 200 and 800, coolant temp is 195-200.

On the ESC diag walkthrough in my shop manual, I did get to the last step where it says to put 12V on the knock sensor pigtail, and if knock is indicated, replace the knock sensor. I've ordered one, but if an ESC Count of "3" isn't triggering any timing advance, I'd like to avoid spilling coolant everywhere to change the knock sensor.

 

[Schurkey]

On the ESC diag walkthrough in my shop manual, I did get to the last step where it says to put 12V on the knock sensor pigtail, and if knock is indicated, replace the knock sensor. I've ordered one, but if an ESC Count of "3" isn't triggering any timing advance, I'd like to avoid spilling coolant everywhere to change the knock sensor.

Knock sensor should trigger timing retard, not timing advance.

There's a moderate chance that the water jacket is so plugged you could pull the knock sensor out and not spill a drop. It used to be fairly common that to get the block to drain, you'd have to punch an awl or screwdriver into the drain hole to poke through the crap laying in the bottom of the water jacket.

 

[studigggs]

Just to close this out, I was able to swap in a new Delco knock sensor (PN 213324) and only lost a pint of coolant between the wet sleeve and Prestone facial. I put a new pigtail on as well as the plastic was brittle on the original. Test drive shows no knock at cruise. I get ESC Counts of 1-2 during hard acceleration. Overall it seems to accelerate better between 40 and 70 mph which is where the trough was prior to replacement.

Never would have been able to diagnose this without a scan tool as the 'bad' or overly sensitive knock sensor never triggered a CEL. The only downside to this endeavour is that now I'm obsessed with scan tools. Been watching South Main Auto Repair on YouTube regularly. I had no idea diagnosis was so complex.