Knock sensor problems
 

Ok, I did a 94 T/A swap into a car, and I am running into a few problems. The car had severe trans problems but the motor was fine (no codes). So I send a new PCM to the programmer and when he sent it back, I am throwing the Knock sensor code, and the canister purge code. Ive got longtube headers on the car, and 1.6 rockers, and the LT4 K/M but for some reason it started throwing the codes after he reprogrammed.

My question is, what could cause these? The car set in the driveway untouched from the time it was perfect, to when it started throwing codes.

I had the canister purge deleted from the PCM, so could the fact that its throwing that code be a programming error?

Thanks in advance guys

Re: Knock sensor problems
 

Please give the exact codes you are getting.

Re: Knock sensor problems
 

#'s 26, 43, 95, 96, 97

Re: Knock sensor problems
 

Have you checked fuses or checked the EVAP solenoid, knock sensor or VSS for power? 95 and 96 don't show up in my list of codes.

Re: Knock sensor problems
 

Does your speedometer work?
How does it idle?
Does it run hot?
Who tuned it? (so I know to never send my pcm there)

Re: Knock sensor problems
 

43 usaly indicates the a bad or wrong KS, and if you did nothing I would wounder about what happened to your PCM. Do you have the original bin file? if so that is where I would start.

Re: Knock sensor problems
 

Ok, you will have to excuse me to an extent, this is my first experience with LT1's, and fuel injection for that matter.

The scanner I used was a Tech2 GM scanner, that named #95 - Oil Life, and #96- Oil level. These codes were there I believe when I had the last PCM and had all the tranny issues.

It calls #97-4K pulses, #26- Evap Purge, and #43 - Knock sensor

I cannot remember what exactly the EVAP silinoid is, please forgive me there, But if its emmissions related, then its probably gone. I was supposed to have the canister purge, AIR pump, and EGR all deleted.

The speedometer (autometer) IS freaking out, and I havent been able to figure that out, is it related? However, the VSS is brand new.
It runs when its warmed up, and when I clear the codes while the car is running, it smooths out until about 5 seconds later, then the SES comes back on and it goes back to a low rough idle.

Not sure what the BIN file is either (refer to me being new to this above)
I was also told that I may need an LT4 knock sensor (already have the module), but I cant figure on that since the motor ran fine with the other PCM.

I hope I got everything there, let me know if you need any other info

Re: Knock sensor problems
 

I don't think you can use the LT4 KS unless you have two of them and rewire, because they have a diferent resistance (Ask me how I know). When I first started my 383 I was getting a code 43 and it turned out to be I had the wrong knock sensors installed, the parts store had given me 2 of the f-body sensors instead of the corvette sensors. Because the corvette uses two sensors wired in parallel they have a diferent resistance then the F-body. Just to get this straight in my mind, the car was running fine then you sent the ECM off to get it programed and now it is setting all of these codes? If that is the case send it back and have them reload your original bin file. (The bin file is a file that contains your program for the ECM)

Re: Knock sensor problems
 

Well, I emailed my programmer, and asked him to send my old PCM back to me with the tune on it, and I will try that if he will send it. we will see what he says

Re: Knock sensor problems
 

What of these codes might mess the speedo up, because it works very irratically.

Re: Knock sensor problems
 

The 4th gen f-body uses only one knock sensor.

There is no specific LT4 knock sensor. It is the same sensor used on any OBD-II LT1.

You need the correct knock sensor to match the OBD type of the PCM you are running (meaning, the knock sensors are of different impedance between OBD-I and II and cannot be interchanged).

The LT4 knock module can be interchanged on any LT1 PCM from 1994-1997.

Codes 95 and 96 do not apply to the 4th gen f-body. My Tech Page has list of proper trouble codes.

Re: Knock sensor problems
 

My PCM is OBD1, and it must be the right one, because this wasnt a problem before I changed to the other PCM, which is also an OBD1.

Re: Knock sensor problems
 

Just for the he!! of it, pull the harness connector off the knock sensor and (key on, engine not running) measure the voltage from the single pin on the connector to the block. PCM should supply 5.0V. Then with the wire still off, measure the resistance from the single pin on the knock sensor to the block. Should be in the range of 3,500-4,500 ohms. Then put the harness connector on the sensor, and measure the volts from the harness wire/sensor pin to the block Should be 2.5V.

That will tell you if the PCM is supplying the correct reference voltage, and whether you have the correct knock sensor, in working condition. Work on one problem at a time.

Re: Knock sensor problems
 

#97 the VSS (vehicle speed sensor) output signal.

you said you have an lt4KM right?
Did you try sticking the original one back in, to see what happens?