Camshaft Position Sensor

Um,

If it doesn't know there the cam shaft is, how does the computer know when to inject the fuel?

Seems so.... :)

There are two reasons the cam position sensing capability is there:

-Sequential fuel injection requires knowing which cylinder of the pair is on the firing stroke. If the cam position input is lost, the system will revert to a mode where injectors for both paired cylinders are fired at the same time (i.e. not SFI anymore).

-OBD II misfire diagnostics also need to know which cylinder is on the firing stroke, since the diagnostics must have the ability to identify the specific cylinder that is misfiring.

Um,

It seems as though the OBDI cars have multiport fuel injection as opposed to sequential, so they don't need to know where the cam is. Besides, tell me how the computer in an OBD1 car locates the position of the cam and I'll be the first one to admit I'm wrong. But that might have to wait a week since I'm leaving for vacation in FL at noon today :)

I shouldn't have worded the post the way I did. On OBD1 cars it seems they have multi port fuel injection as opposed to sequential, so they don't need to locate the cam. On OBDII cars, when they lose input from the "cam sensor" as you said, they would revert to multi port non sequential injection.

Again, as I said to Kirk, to my knowledge the OBDI cars have no way to locate the cam. I've had my engine out of my 95 twice and pretty much gone over it top to bottom, inside and out, no cam sensor to be found.

I'll back you up on that. I had the same error with my 96 SL1. It went away with aftermarket plugs & wires, then came back. The problem went away for good with Saturn OEM plugs & wires.

Jim Ohio

My 96 SL2 uses both cam sensor and coil pack to determine cam position. Cam sensor is located up on top and behind the starter about $22:00 for a new one at the dealer.

The cam position sensor on the OBDII cars is embedded in the coil pack. There are (apparently) different characteristics that result from putting a spark through a highly-compressed air-fuel mixture and non-compressed exhaust. As I understand it, there is a capacitive coupling in the coil pack to the ignition wires that permits the computer to determine which cylinder fired.

So you probably wouldn't see something that looks overtly like a camshaft position sensor.

That sensor is a crankshaft position sensor, not a camshaft position sensor. It tells the engine very precisely where the crankshaft is. That information, plus simply knowing which cylinder fires, lets the computer know precisely where the camshaft is.

Wow, and Harley boasted when they got rid of the wasted spark setup...

I always suspected GM used wasted spark on the Saturn motor because of the way the coils are on it.

There is no camshaft sensor on the OBDI cars, they fire all 4 injectors at the same time (cheap GM...) and have wasted spark, so they don't need one..