CPS or Imobilizer?

[DarkStar]

Well I got groceries and my car won't start. I'm waiting for a tow truck right now. But it's doing the all good strong crank but no fire. The car threw a pending code for Crank Position Sensor. However I just moved the guts from my key to a new fob, and it's worked just fine.

But, let's say the Imobilizer chip is, not close enough or stopped working somehow... Would cranking it cause a CPS code? Or is the DME smart enough to differentiate the two?

Second, anyone replace the CPS got a pic of its location?

[dghii]

I'd trust the code.

[thstone]

When the immobilizer isn't communicating properly with the key fob, the engine won't turn over at all.

Thus, its most likely the CPS.

[rick3000]

If you tried to turn the car over with a key that did not have the immobilizer chip, the immobilizer would activate and the car would not crank at all. Easy indicator for the CPS, is if it doesn't want to turn over when warm, but turns over fine when cold. The sensors tend to get finicky when warm before failing completely.

It's not a difficult DIY, but can be a little annoying reaching up through the rear suspension. You can find more detailed info with a google search, but Pelican has a little info: (purple arrow in picture 4):
Porsche Boxster Engine Sensor Replacement - 986 / 987 (1997-08) - Pelican Parts Technical Article

[Gelbster]

The usual CPS diagnosis is : "Does the rev counter needle bounce a little when you crank the engine? If it does bounce the CPS may be O.K. Definitive test is to measure the resistance of the CPS. The CPS resistance deteriorates as it nears the end of it's life JFP posted the ohms-spec.
http://rennlist.com/forums/996-forum/766125-lets-discuss-crank-position-sensors-for-a-moment.html

[specboxCO]

Originally Posted by DarkStar

Well I got groceries and my car won't start. I'm waiting for a tow truck right now. But it's doing the all good strong crank but no fire. The car threw a pending code for Crank Position Sensor. However I just moved the guts from my key to a new fob, and it's worked just fine.

But, let's say the Imobilizer chip is, not close enough or stopped working somehow... Would cranking it cause a CPS code? Or is the DME smart enough to differentiate the two?

Second, anyone replace the CPS got a pic of its location?

CPS usually fails intermittently. Will refuse to fire, then work for a while, die while driving, then spring back to life etc.

This is definitely a failing CPS, not an immo problem. CPS is on the rhs of the engine where it meets the transmission bellhousing

[DarkStar]

Thank you all. I would have posted back earlier but I had some work to do when I got the car home, I had it packed with groceries! So thanks for all your input. I was googling a lot of this information while in the tow truck ride home.... It does look easy enough. Damn sloot started as the tow truck driver was lowering the flatbed.... However it must be very picky, because it was outside for a few hours while I was inside grocery shopping, so it cooled down considerably. Then the 30 minute wait time for the tow truck.... which took like 45 minutes since I had to make sure that the tow truck could get on base.... and then the hourish ride home in 5PM Rush Hour Traffic.

I wish I could find it cheaper than 85 bucks, but oh well. Whatever the girl needs, can't be having such a beauty requiring a tow.

So once again, THANK YOU ALL

[Gelbster]

So you confirm you really found the problem:
When you remove the old CPS ,suggest you do a simple comparison test between the old and new.
Simple Multimeter test to observe if it is within spec -should be 800-1000 ohms at 20 deg C.
An deteriorating CPS will be in the low 800's or below. If you heat it to 150 degrees F or more it may be fail completely ,then recover when cool.
If you post your results it will help others chasing this common problem and may enable us to help you further.
If you want more tech:
http://rennlist.com/forums/996-forum/821112-crankshaft-position-sensor-diagnosis.html

[jcslocum]

The CPS is on the right/pass side, in a slot between the trans and the engine. I have pics but can't get to them right now. If doing it on the ground, I think it might be easiest to pull the rear wheel and go at it that way. It will be in front of the rear wheel straight in, held in with a Allen bolt. The plug is on the back of the area near the cam plugs. The wire is like 14 inches long.

As I recall, there is a BMW one that is exactly the same in the $55 range. My memory on this might be bad tho. Do a google search and good luck.