I haven't had a chance to change the wire that runs from the back of the PCM to the KS in the block. That is what has been causing my DTC 43. I replaced the KS, KM(w/LT4), and I checked the PCM for 5V. I programmed out my KS system in the PCM and was wondering what will happen if I drive with it like this. I was told that it wont be that bad because my car isn't heavily modded yet(cam, heads, blower, so forth). I read some others posts and wasn't sure about what exactly can happen and what are the chances of it happening.

For those of you guys that have changed the KS wire, how involved is it? It looks like that hardest part is re-running it through the plastic tubing that its located in. Also what gauge is it?

 

Well, if the pcm sees no knock, no knock retard. If you get lower octane gas or a bad batch and start spark knocking like a double-bass drum, then theres no way to retard it. Though you did say you programmed out the ks, so try programming out some timing to be safe. Chances seem low, but eh. Goodluck bro.

 

Say you have bad batch of gas and you start spark knocking and pinging, what will happen since the computer cant retard it. I'm having a hard time understanding it. What happened to engines that werent epuipped with knock sensors and PCM when they had bad gas?

 

there timing was set alot lower to compensate for those situations.

 

I'd keep the KS. It'll save your ***. I had two valve springs that broke, and I got an SES light. Scanned my pcm, and got code 43. I figured it was picking up knock from the rockers. Thought maybe they needed adjustment. I pulled off the valve covers and saw two broken springs. Luckily, they had not yet dropped the valves.

 

I would also keep the knock sensor, with hot wether and a bad tank of gas you could be in for some trouble. Also doesn't the Granatelli MAF make our cars run lean anyway? I thought I heard that somewhere before.

 

If I understand the post correctly, you have a bad wire from the PCM to the KS. If the PCM can not "see" the knock sensor, because the wire is bad or the sensor is dead, it defaults to a table/calcualtion that results in large amounts of knock retard. It does this to protect your engine from damage when it can't get a reading from the knock sensor. You're going to have knock retard at idle, and up to 15* of knock retard during normal driving and high loads. That will protect a lightly modified engine.

Do not "program out" anything. Just leave it the way it is, and your engine will be protected. You will lose performance, but no big deal, if it protects your engine.

 

I thought that if you get code 43 it is because the resistance in the KS system is not correct. I read some posts on here and they are saying they recieved code 43 due to exhaust rattles, loose motor mounts, roller rockers. The only thing that hasn't been replaced in my system is the wire. Everything else in the system has been checked or replaced(LT4 KM, new KS). Should i be checking for stuff that is rattling or something of that nature. I need help, my car has been not running correctly for quite some time. This morning I reflashed my PCM wiht the KS system programmed out and the SES light went away and the car ran normal as it did before I got code 43. I hope it is the wire because I'm running out of ideas. Before I reflashed it this morning I couldn't even pull my car out of the garage without it dying.

 

You get DTC 43 for circuit voltage outside of spec. That means if the knock sensor or a wire shorts out, and you have near "0" resistance (0V), or if the knock sensor or the wire has an "open" (infinite resistance, 5V), you get DTC 43.

You will not get DTC 43 from "false knock" caused by rattles, or any other kind of knock signal from the sensor, as long as the resistance is in the correct range. The knock "signal" is a sinusoidal AC frequency riding on the resulting 2.5V bias voltage in the circuit. You don't get voltage outside the acceptable range just because you have a signal from the knock sensor.

Its so easy to check, from your comments I assumed you have checked it. Key on/engine off, pull the harness connector off the sensor and you should have +5V on the connector. With the harness still off, probe the single pin on the sensor to ground at the block. Should read 3.5 to 5.5Kohms (93-95 only). Attach the connector and the sensor should pull the voltage down to about 2.5V. Anything below 1.5V or above 3.5V will set DTC 43.

 

Fred is correct. Code 43 WILL NOT be set due to false knock, rattles or other noises or vibration. From my experience, the code 43 will be set for one of the following reasons:

Problem with knock sensor (the sensor in the block)
Problem with the wire going to the knock sensor
Problem with the knock module (in the PCM)
Problem with the PCM

My suggestion is to find the problem and get it fixed.
I ran my car with the knock sensor disabled for a while (and I might do it again soon) but I only use my car for racing and I do thorough testing on the dyno and on the street before I decide to disable it.

 

I have mine programmed out as well. There was a time you know, when cars didn't come with knock sensors. If you hear rattle, get out of it and fix it.

Pull the plugs every once in a while and look for detonation.

 

I have the knock sensor disconnected (not really useful with a solid roller cam). And I don't use the stock PCM for anything but the VSS and the IAC (MoTeC ECU version that I have can't operate a "stepper" type IAC, only a PWM valve). So... with the ScanMaster watching the stock PCM, I get to see what values it would be using for knock retard without the KS connected. There are some pretty big numbers, 9* to 12* appearing frequently. Of course I also get codes for no injectors, no MAF, no EGR, no ICM/coil, etc. Amazingly, even with all those codes showing, the PCM is apparently still capable of running the engine. Sensors like the MAP and Opti are paralled to both computers, and where its not possible to run parallel wiring (IAT, coolant), I run duplicate sensors.

Not running a KS leaves you at risk. Since I'm spraying a 300-shot, there's a lot of dyno time invested in getting the tune correct, and when I spray the big shot, I will only run fuel pumped directly from the drum of VP Fuels C16 that I keep in a shed in the back yard, so there is no risk of getting a bad tank of fuel somewhere.

 

Thanks for the replies, ill let you know what happens.

 

Running without a knock sensor leaves you at risk if you don't know what spark knock sounds like. To the more expereienced guys the knock sensor with a good tune does nothing but could possibly make the car inconsistant going down the track.

 

I had mine programmed out about 8 months ago, I've put on maybe 2500 miles on the car since then. I would NOT recommend doing this UNLESS you are certain that it is false knock. You need to check everything, especially exhaust and valvetrain adjustment. Continually log the car after you make any adjustment (I used Datamaster), then before you program it out, run 100 to 105 race fuel and log the car to see if your knock goes away. If it doesn't go away (like mine) make your decision. In my case, even with the LT4 KM neither I or Jeff at CAM could find out where my knock was coming from--but we were confident that it was false knock. Also, my car will only see 5,000 miles a year so it is not my daily ride. BTW, I noticed a big difference with it programed out, I was pulling between 7 and 12 degrees during acceleration.