x phantom x

iTrader: (14)

Eh, okay. Again, thanks for trying to help, but you're providing BAD information. As I said, I DO have the service manual, and I DO know how to read.

And I quote:

"The Camshaft position sensor determines whether a cylinder is on a firing stroke, or an exhaust stroke .... The PCM uses this 1x signal along with the 24x signal from the Crankshaft Position sensor in order to determine crankshaft position and stroke .... If the CMP sensor is malfunctioning, the engine can still start. The system attempts synchronization and looks for an increase in engine speed during cranking, indicating the engine started. If the PCM does not detect the increase in engine speed, it will assume it incorrectly synchronized (lack of knowledge of the intake/exhaust stroke, due to malfunctioning cam sensor) and re-syncs to the opposite stroke. A slightly longer cranking time on occasion, may be a symptom of this."

Basically, the crank sensor determines when the piston is at TDC, and the CMP sensor determines whether it is the intake or exhaust stroke. Obviously if the PCM sparks on the exhaust stroke, it will never start and most likely just backfire (as my car does), but if it guesses correctly on the first try the car will start as if everything was fine (as it is does) ... it is also saying that if the PCM initially guesses the cam position wrong, and senses that it didn't start (using the crank position sensor), it will flip the spark/fuel to the other stroke, and the car will then start after the short delay (as it does).

In short, this diagnostic tells me that the crank sensor is obviously fine, and the cam sensor is obviously wrong. If the cam sensor was working, and the crank was not, the car would run fine, since the PCM can get all the info from the CMP sensor, and seemingly just uses the crank sensor as a redundant system, so that the car will still start incase one malfunctions.

Edit: Another way I am sure of this, is that I just went out and disconnected the harness to the CMP sensor, and the car still behaves exactly as it has. If the crank sensor was the culprit, the car would not start. Go out and try it on the vette if you want to see for yourself.

x phantom x

iTrader: (14)

.
Fixed the problem today ... cam sensor wires were crossed due to the LS2 cam sensor harness .... flipped the wires and everything works great.

Thanks guys.

tomulrich

iTrader: (2)

95 percent of the info put on this forum is incorrect. If you read my thread above...I disconnected the Cam sensor on my neighbors 2001 vette.....tach/gauge worked fine.

Maybe there is a difference in PCM's.

By the way....in your post where you quoted the GM manual....I see nothing that tells me the tach signal is derived from the cam and crank signal.
Does it tell you what the pulse per revolution is for the tach? Do you know?

The information is not wrong as you stated.....there just may be differences in PCM and gauge clusters....

Tom

tomulrich

iTrader: (2)

The who time I have been talming aboutthe LS1....not LS2 .........maybe that is the difference?

x phantom x

iTrader: (14)

Ug dude, your information was wrong .... please give it up. I JUST CONNECTED THE STUPID WIRES THE OTHER DAY AND MY TACH WORKS, OBVIOUSLY THAT WAS THE PROBLEM!!!!

The post I was talking about was for my 402ci LS2 .... you talking about a different engine (on a completely different car/platform nonetheless) makes your information wrong. If someone came in here and started making comments based on a 5.0L Mustang engine claiming it was correct, it would be the same situation.

You're in the LS2 section, the initial post was with regards to an LS2, and you argue with us that we are wrong, while giving wrong information the entire time.

Btw, it is entirely possibly that the vette receives it's tach signal from a different place .... which is why 3 people told you that your information is not exactly relevant since it is for a different car.

Like I said before, I appreciate the attempt, but the problem is fixed and your solution was not the correct one. Thank you anyways.

Slowhawk

iTrader: (12)

You should of went by my first post,would of saved you alot of time

x phantom x

iTrader: (14)

Well, when I read your post, I thought you meant the wires were crossed when they were extended, which is why I originally redid them. I didn't realize the LS2 CMP sensor actually has the wires backwards with regards the the LS1 sensor.

Thanks though

Slowhawk

iTrader: (12)

Sorry,I did give a short answer and should of explained it better

x phantom x

iTrader: (14)

Hehe it's okay. Still figured it out eventually.