SES light on intermittently usually at lower speeds running around town. Goes off when at highway speed. FSM shows it to be a knock sensor problem. Anyone have any input to common causes for it?? I haven't gotten around to looking at the connections , just replaced both knock sensors last summer so figure they should be fine. I will look at it this weekend, but thought I'd check it here w/ the experts b4 going much further. Thanks.

 

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


I had code 43 last yr and once this yr, both the time i did not checked anything just replaced ESC (on p side square thing at extreme corner) and KS too. solved my problem,

I bought ESC at gmpartsdirect.com.

 

Only the '85-'89 use the ESC module between the knock sensor and the ECM; '90 & up connect the knock sensor signal directly to the ECM.

-verify that there is no contact between exhaust system & frame or other metal to metal contact that could trigger the knock sensor
-verify that the knock sensor connector is attached to the sensor
-disconnect the sensor and, with ignition On, you should measure 4-6Vdc at the connector
-measure the resistance of the sensor, it's ok if in the range of 3,300-4,500 Ohms

 

I crawled under it and towards the rear where the knock sensors, 2 if I recall right....The slip clip connection on them were gunked up. I cleaned them with electronic cleaner, slipped back on, and wala, lights went out, code went away. Might of been a fluke, but worth a slither under there to check them out.....

Swampy