poposhad

I have a 94 z28 stock. I am getting code 43. i had checked the resistance of the knock sensor and it was ok. i do have an LS sensor which i believe has a higher resistance just in case. The previous owner had replaced the pcm and i was wondering if he had replaced it with the wrong year or model. i know some cars have two knock sensors and if he used that pcm on my car it would cause code 43. i know it could also be the module on the pcm. the pcm has a barcode and the numbers are EM8051 US and also on the bottom side it has 91769 36415. also another sticker has the following numbers BL1215, and SL1104. any suggestions, i would like to verify the pcm first before replacing the module

Injuneer

Did you check from the unattached harness wire to the block to verify you have 5.0V reference? With the wire connected to the sensor, did you check from the wire to the block to make sure you have between 1.5 - 3.5V? The 94 diagnostic sets DTC 43 when the voltage exceeds 4.10V for 5 seconds, or is less than 0.78V or 5 seconds. Was the sensor resistance between 3,500-4,500 ohms?

There is a separate code for the knock module (DTC 47). Although DTC 43 can be the result of a faulty sensor, faulty module or faulty PCM.

poposhad

thanks for the reply, when you said unattached wire harness, do you mean disconnect the wire harness from the sensor. currently i dont have an unattached wire. i did check the resistance of the sensor and it was within range. when you say to check the voltage from the wire to ground, i have to pinch the wire with the probe in order to to that correct. i guess what you are saying is to disconect the sensor wire and verify 5 volts. Thanks for the great help. i will do that now. also, i guess my pcm has a barcode sticker that doesnt give me the correct numbers to verify the year, i will double check anyway, it does have the knock module, i want to verify that the replacement was done right. do you have any suggestions. again thanks for your time and help.thank you

Injuneer

Yes, pull the harness connector off the sensor. Probe the terminal at the end of the harness connector with the red lead from the meter, and touch the black lead from the meter to the engine block. Make sure you have a clean area on the block (no paint, no grease, etc.) to touch the black lead to.

When you reattach the harness connector to the sensor, you may need to pierce the harness wire insulation with a pin to contact the wire, and attach the red lead to the pin.

poposhad

thanks for the reply, i have 4.92 volts from pcm / sensor is 3.8 k ohms / voltage with sensor in the loop is 2.42 volts

Injuneer

Did you clear the code before you rechecked to see if it came back?

poposhad

i cleared the codes two nights ago and it would come back on, code 43. the car would change back and forth when idling because of the code. is it supposed to do that or keep the ignition retarded all the time. is it possible to check the module by resistance to see if something is out or has the wrong expected value. thanks
there are no stickers with part numbers on pcm, how can i determine if it the right one. the previous owner told me they had replaced it when they were troubleshooting a problem.

Injuneer

What does this mean:

"the car would change back and forth when idling because of the code."

How would it "change"? Did it "change" when the SES light came on? What exactly happened?

When DTC 43 is set, the PCM calculates a spark retard based on engine operating conditons. It will retard at idle, and at other times can pull up to 15* of timing. That would be noticeable while driving.

poposhad

sorry about the wording, after clearing the code, i started the vehicle back up. the SES would come back on and after that. i checked the code and it still was 43. i did notice a change in the engine and forth from being retarded to normal, i guess i was wrong. maybe that was after clearing code and restarting it. i will double check with my neighbor who was with me.i went out now and started the car, there was no fluctuation from the engine and still sounds as if it is retarded. its raining right now so i couldnt drive it around the block to test it.

poposhad

i checked the voltage from the wire to ground and i still got 2.42 while the engine is running. even though i got the right voltage could my knock module still be at fault. do you know any weird things that could also trigger code 43. i am thinking it might be the programming or wrong pcm. your help is greatly appreciated thanks again.

poposhad

forgot to mention , after we cleared the code and restarted the car, the idle to change like it goes into limp mode and stays there in that mode.

poposhad

thanks for all the help.

the problem has been solved. the pcm needed to be flashed with the standard calibration. the pcm was purchased from advance auto parts and was never programmed for the car. it would run but code 43 was always coming up. after programming, the car ran great compared to before, and no more code 43. wow.

thanks again