I am getting a code 43. With key on, should there be voltage going to the knock sensor wire? I got nothing. Knock sensor is new.

 

From the Code 43 test procedures on pp 6E3-A-52 & 6E3-A-53 of my '88 FSM, it appears that there should be no voltage on the knock sensor wire.

Further, if you tap on the exhause or engine block near the sensor it should generate a brief +12Vdc signal on the Dk Blue wire.

If you see a voltage on the the Blk wire from the ECS the ECS is likely defective.

 

Ok, on another corvette forum, I read that there should be 5 volts..... dont know.

 

http://www.chevythunder.com/maf_esc_module_code_43.htm

 

Did you have the code before the sensor replacement?

Can you put an ohmmeter on the (disconnected) new sensor? The older C4 sensors had a 100kOhm internal resistor across the crystal (for use with the external ESC module), while the later ones IIRC had a 2kOhm resistor (for the ESC circuitry mounted in the ECM).

Occasionally the harness connector loses its electrical integrity to the sensor if it's messed with too much. I've been told it's only designed for a couple of insertions/disconnects.

I'm trying to remember what vintage L-98s had a software algorithm that would add in a little extra spark advance at some speed/load points to purposely make the engine knock slightly, and then the ECM would look for a signal transition from the ESC module to confirm that the sensor/module heard the knock. The method had a few limitations in that if the engine had a low limit compression, or was running some decent premium fuel, a bit excessive EGR, or if it was just a humid day, any of these factors could prevent the engine from knocking as intended, and the ECM would think that there was a functional problem with the sensor or module. Later ESC units made an actual electrical measurement to determine the integrity of the system.

 

Thanks for the response, yes I had the code before replacement....I replaced motor in 85 vet and used the old knock sensor that I removed with channel locks, before I knew how sensitive the darn things are. When testing fresh 350, I had a code 42 and 43, not at start up, but on test drive. I replaced knock sensor and lost the code 42, but every once in a while will get the 43 on drives not on start up. I am having issues with the car stumbling in cruising speed around 15- 20 mph , but will idle smooth and has great acceleration. I have had alot of responses with different fixes. I have tried most of them with no luck.... In the process of installing motor I replaced injectors.... I was told they are too small 21lbs, but was told if I raise the fuel pressure they will be ok.. nope, still the same.

 

..... L98 Knock sensors have a piezo crystal in them that generates its own electrical current when vibrated ...........