blue 79 Z/28

95 camaro, fully built AI 383 LT1, tuned by fastchip. has an engine light on, scanned it and its the code for knock sensor. i am not running one, and i told the tuner i was not running one. do i just have to live with the light? will it affect the cars tune with that code active? it clears and comes back right away. when i start the car, even when cold the high and low speed fans are active, could this be because of the code?

bobdec

No knock sensor should throw a DTC 43, it will pull max timing (10* stock setting) therefore cause lower performance.. I suggest adding it back in. You could lower the timing that is pulled by doing it in a tune. IMO it's a gamble that a lean condition failure down the line won't cause engine damage. Yes the DTC runs the fans to save the engine as it is not monitoring knock. Seems a small $$ investment compared to what you have already spent on a 383 build...

Injuneer

Check to make sure they didn't just stick a resistor in the harness connector. The code sets when the circuit voltage is outside the range of 0.78 - 4.10V (94 shop manual specs for DTC 43). Loose wire, etc.

From reviewing data logs for people, I've seen that the max allowable knock retard in a factory program appears to be 15*. And when DTC 43 sets, the knock retard is not a fixed value, but a variable value, which is based on engine load (MAP) and RPM.

In any case, you don't want that code to be active.

You could try sticking a resistor in the harness connector, to produce a voltage reading in the correct range, in order to eliminate the code without getting the program updated. The 93-95 knock sensor has a nominal resistance of 3,300-4,500 ohms (94 shop manual).

96capricemgr

I would email Ed and ask him to take a look at the tune, maybe he overlooked turning it off.

blue 79 Z/28

i built the car and the harness from scratch, used to be a 3.8L v6 car. just did the full conversion and swap. when i got the cpu tuned i specified i was running no knock sensor. i didn't know it couldn't be removed by the cpu alone. the engine has no knock sensor installed and i removed the wire from the harness to streamline it. DTC 43 is the only code it has, runs mint otherwise. what would be the most effective way to eliminate the code and have the cpu not use the knock sensor at all, i do not want the knock sensor active to pull timing. im sure fastchip zero'd the values for the knock sensor. can i install a resistor and wire it/ground it and tuck it away somewhere or does it have to be the sensor in the block and wired in? i can just run another wire from the computer separately easily enough.

blue 79 Z/28

so you can turn it off in the computer and the code wont trip?

bobdec

Getting rid of the SES light can be done by disabling the DTC 43 diagnostic in the tune. SOMETIMES disabling the diagnostic does not stop the PCM from processing what it sees as incorrect input. I can not comment on how the PCM will react to a dead knock sensor sensor input. Fred's post #3 , adding a 3300-4500 ohm resistor between PCM pin D22 (knock sensor circuit) and chassis ground should eliminate the DTC and trick the PCM into thinking a knock sensor is installed and no knock is being detected. That's the best solution. It could also be done with a tune, by turning off the DTC 43 SES diagnostic AND setting two tables 'Max Knock Retard in PE' and 'Max Knock Retard not in PE' values all to 0. The stock retard settings look at RPM in PE they vary from 9-12* and look at Map in non-PE they vary from 0-15*. I used 10* as an average in my earlier post.

Injuneer

I didn't say it could not be eliminated by tuning it out. I indicated that the resistor is a way to do it if you don't want to get it reprogrammed.

96capricemgr

Honestly with a hydraulic cam I would keep the knock sensor. Ed can desensitize it but keep it functional and this adds some protection should you run into unforseen issues like bad fuel or low fuel under power starving the engine some.

blue 79 Z/28

thanks for the input guys, i will look at it today. i will try the resistor trick to start. what resistor rating should i use? how many watts i got a pack of 1/8watt resistors i could parallel a few. i would think the sensor circuit is low current enough. i used these same ones to bypass the VATS key, thoughts?

Injuneer

The resistance of the sensor you are replacing is in my post. That's what you want to match. At 5 volts, and a resistance in the range of 4,000 ohms, the current draw will be minimal. 1/8th watt will be fine. Remember, when you put resistors in parallel, the resistance of the circuit is reduced. You need to put them in series if you want them to be additive.

blue 79 Z/28

so i put the resistor inline, 4400 ohms on blue pin 22 to engine ground, scanned with the snap on motis. no codes or engine light now. started the car, ran good at idle for a min. put the car in reverse, got about 5 feet and the car just shut off. wouldn't restart.cranked over a bunch, caught once and ran like crap and was pinging even with no load on the engine at 2500rpm in park. then it died again and i haven't been able to get it started again. rescanned with the motis and no codes still, all sensors are reading on the engine. any thoughts? my car is now stranded

Injuneer

Did you check the sensor wire to make sure it didn't come loose and short to ground?

blue 79 Z/28

it was grounded with the resistors in line. engine light went off and ran for a min or so. i even unhooked it and completely reversed what i had done, and still nothing. no codes at all either. could i have fried the computer? the motis is still communicating with it with zero issues and shows all sensor values. i need to check for fuel and spark first and go from there i guess....

Injuneer

Did you simply use the blue wire to the knock sensor to complete the circuit, or did you get into the PCM connector pins? There is nothing inherent to what you did that would "fry" the computer, unless you somehow you possibly applied 12V to the circuit.