aminnich

I recently replaced the well worn hi miles LT1 in my '95 coupe with a LT4 that was modified with porting, cam, lifters, etc. I had the PCM tuned, new knock sensors (LT1) on both sides and and a lot of other new parts, including egr/air delete and long tube headers.

Issue is a code 43, knock sensor code every time I start the car. Driving with a scanner hooked up I am getting no knock counts. I am thinking the cam is causing the knock code at start and idle as it has quite a lope, but I am open to any suggestiions.

sailorsteve

I believe the LT4 uses a different knock sensor than the LT1. You can find out by looking up both parts on a vendor website to see if the two numbers are the same.

aminnich

Thanks for the reply. You are right, but both of mine are LT1 sensors and both are new.

sailorsteve

I thought I understood you to say you had LT1 k/sensors in an LT4. If this is correct, this could be your problem.

aminnich

No, the knock sensors are matched up to the PCM, which is a 95 PCM.
I should also add the wiring has been checked and no problems found.
I also tried inserting an LT4 knock module in my 95 PCM and that didn't help either.

jaa1992

Which side is the code 43 for?
I know its a pain but maybe try another sensor on that side?

aminnich

How do I determine which side?

sailorsteve

Code 43 is for knock sensor fault, does not distinguish between left and right. But, if you are getting no signal, the problem is likely common to both sides. One issue with these sensors is, if there is too much sealant on the threads, the signal is not generated. New knock sensors typically come with sealer already on the threads, if you add more, or use teflon tape, it could interfere with the signal, as the knock sensor works by grounding on 5v. or less.

aminnich

Steve, you are good. I found that out after I put them in with teflon tape and had to pull them back out and take the tape off. They are getting a good ground to the block now and the 5v feed is good to both of them. The OHM reading is about 9600, which I understand is in spec as well.

sailorsteve

aminnich

Steve, thanks for the assistance. Jim, I am about down to replacing new knock sensors with another new sensor one at a time to see if one of the already new ones is bad or maybe I got sold a wrong part. Otherwise Bryan has offered to program the knock sensors out of the PCM, but I am not keen on that idea.

ddahlgren

Is the starter shimmed correctly or are there issues or changes in flywheel / clutch assembly. I tried years ago running knock sensors on a twin engine boat with outdrives and the outdrives set them off when in gear.

aminnich

Interesting thought. I moved the starter and flexplate off the LT1 to the new engine, also a new 2500 stall convertor coupled to a freshly rebuilt 4L60E. No starter problems and no vibrations.

dizwiz24

I believe code 43 may not just be knock sensor, but also ignition module as well.

Thats the thing that the ignition coil is bolted too.

i had a code like his once on my 93 lt1 and it ran in some kind of reduced power output mode (so it felt) until I replaced the igntion module that the coil was bolted too. Code went out and no probs ever since.

Also, people mention teflon tape or excessive sealant is a bad thing...

Whereas over at camaroz28.com they think thats a good thing, on heavily mod'd motors, because it insulates the knock sensors from being set off due to 'false knock'.

Not sure how they think that would effect the ground (maybe the rig a seperate wire outside the threads to a ground?)

aminnich

Actually reduced power is not a problem. I ran it against my son's modded C5 that is putting almost 400hp to the ground and mine is quicker. On the 1-2 shift and the 2-3 shift it burns rubber. Just the service engine light due to the code 43 is annoying, but certainly not hurting the performance. Also, mpg is almost 3mpg better than with the old engine. Thanks for the reply, every bit helps or gives me something else to think about.